Maybe you don't get it because you're using the complaints as a strawman. No one is saying that every single gimmick should be in every new game. The complaint is that the gimmicks are just that - gimmicks - that feel cheap just to market each new gen as something different, but often come out feeling half-baked and half assed, and then get thrown out by the next gen when some of them could stand to stick around and be improved upon.

Some definitely needed to be (or need to be) left behind because a newer feature came long to improve upon them (or GF at least thought so even if this wasn't the case), but others are cut for no good reason. Like Kneetos said, GF could have really put in the time to make contests a significant fixture of the series; even back in the early days of the anime, contests seemed to be an important part of the Pokemon world. I remember when they were first introduced in R/S, I thought they would continue to improve in future games and imagined that they could become an alternative to actual battles, and Nintendo/GF could market that for the people questioning why their selling games about kids forcing animals to fight. But nope, they were gone, then made a brief comeback tour for the R/S remake, then gone again.

What I don't get is why anyone would want to continue paying full price for new games with less content. Not even talking about features/gimmicks here, but a limited Dex. Gen 7 handled the National Dex nicely; limited the Regional Dex and what you saw as you went through the story mode, but opened up more mon after beating the game for those who really want to go the extra mile. And even if you couldn't get a mon within the game, everything was still coded into the game and you can trade for it. Literally everyone got what they wanted. Instead, you want less access to content. That's like saying that sports games shouldn't feature full rosters of teams and just focus on the stars and rookies that year.

That really isn't the impression I get whenever people complain about cut features, but if that is what you believe, I won't necessarily argue with you. Some of the gimmicks are a lot of fun and add to the gameplay and I don't think there should be any complaints about a game specific feature in that regard. On the other hand, some gimmicks suck. For example, Gigantimax was a garbage gimmick (and generally Sword/Shield was a garbage game).

From the sounds of it, Terstallize is a much better gameplay gimmick. From what I gather from the presentation, the Pokemon keeps their original moveset (switching to the simpler Dynamax moveset always sucked, because it removed what makes each of the different moves interesting) and being able to gain new typings and STAB bonus modifications does significantly change how certain pokemon can be used. Visually it isn't the most interesting gimmick (Gigantimax generally sucked, but some of the Dynamaxes were cool (if only they didn't suck to obtain)), but it seems like it will actually make battling more interesting, which probably puts it below Mega Evolutions but above the other game specific gimmicks in my book.

As for the Dex, one of the best things about the core Black/White game was that every time you ran into a pokemon in the main game, it was something you had never seen before in previous games. You aren't running into 1000 Zubats and Digletts every time you enter a cave, you are seeing something new (although the designs weren't always the most interesting for these new Pokemon). That gave the games a very distinct feel that truly made you feel like you were seeing something new instead of just a rehashing of the same old thing. I get nothing out of seeing a Ratata again and again and again, but I do get excited about seeing new Pokemon.

A more limited Dex also allows the games to do more with what they have (while GF often doesn't capitalize on that ability, they also have never really leaned into that, including about 650 Pokemon in S/S+DLC). I see people complaining about Pokemon battle animations and field animations all the time. As such, I would much rather a game focus on making 100 Pokemon's animations unique and interesting than a game which focuses on putting in 900 Pokemon with the same old cookie cutter animations. Again, this isn't something that the games always capitalize on even when they utilize a more limited set of Pokemon, but if I could choose that trade, I would pick a more limited Dex every day. 

The size of the Dex is a huge limiting factor to what you can do with the games, and throwing in the same Pokemon we've seen a million times before makes the experience feel like something I've experienced dozens of times already. I want a game which focuses on giving me the most polished, most fresh experience with a limited number of Pokemon rather than a game which carries around the bloat of almost a thousand Pokemon.

Sports games kind of highlight this problem of bloat by giving you big rosters stuck into cookie cutter games, that sell you on little more than a roster update every year. I don't want Pokemon to be the kind of game that sells you on a roster update every year. Pokemon games aren't quite at that point, but they also aren't at the point where they are providing a focused but polished experience. They are full of bloat so I won't really begrudge them for paring some of that back.

Funny that you mention Black/White, the generation that technically had the most "new" mon, but the majority of them were blatant ripoffs of Gen 1 mon. Timburr line = discount Machop line, Trubbish = discount Grimer, Sawk & Throh = uglier Hitmonchan and Hitmonlee, and so on. To each their own, but to me and many others, Gen 5 felt very uninspired.

Like I said, nothing wrong with limiting the Regional Dex. I feel like Gen 7 handled this better than any other game. The majority of new mon (regional forms count as new mon in this case) really felt like they belonged in Alola and helped tell the story of that land, like the Alolan Raticate/Gumshoos rivalry, and the fairy mon that looks like a lei but I can't remember the name. But at the same time, those games didn't limit your access to any other Pokemon. If you really wanted to collect them all, either as a completionist or for battling purposes, you could collect them all. That is more content that is completely optional. Why wouldn't you want more optional content available to the people who want it?

More Pokemon doesn't mean more bloat and less polish. Pokemon isn't Smash Bros., where Sakurai meticulously fine tunes each fighter for balancing purposes. I guarantee you that GameFreak don't give a shit about that kind of balance. If you want a polished, fresh experience (lol, why are you playing Pokemon then?), then you look for that in the story mode. Then after the story mode, why can't the rest of us have more? The latter doesn't hurt your experience in ANY way. Again, we have proof of that already in previous games.

My argument has never been that a limited 'mon game couldn't be done better. I admitted in my last post that the designs in B/W weren't always the best, even. My argument is just that a full Dex isn't inherently better and there is a trade-off at hand. There are plenty of reasons to think that the game could be better if it was more limited, some of which I detailed previously. 

The core of it is that every Pokemon in the game takes some amount of dev time. Having more Pokemon does hurt my experience by sacrificing dev time that I feel could be better used elsewhere (and with this effort I am asking for, the amount of effort balloons as more Pokemon are added). I would personally rather a game that focused on other means of providing a fuller, more polished experience than a game which spent that time making sure that 1k Pokemon are all jammed in.

Sure, it isn't as detailed as Smash Bros, but it isn't hard to imagine a Pokemon game which put more effort into polishing the Pokemon's battle animations, because that game already exists in Pokemon Stadium (which has much more limited movesets and a smaller roster and was heavily limited in scope). Compare the animations in that game to the animations and S/S and they have way more personality and individuality. When a Pokemon does a kick, it looks like they are doing a kick. Again, they aren't perfect, but I don't think the level of animations you are getting from Pokemon Stadium is something you can really expect when there are 1000 Pokemon each with a total movepool around 50 moves. 

In my opinion, the "right direction" for Pokemon is the one which focuses on polish and details, not the one that focuses on numbers. 

EDIT: I also just want to note real quick, S/S had little excuse to not include more Pokemon. While it likely did save them some time and allowed them to use resources elsewhere, it really didn't show as that game did not look or play very well. So just to clarify, there are three options imo:
1) Less pokemon with a lot of polish
2) More pokemon with little polish
3) Less pokemon with little polish

Obviously 2 is going to be preferable to three. I wouldn't argue that. However, if we are talking about the direction we want Pokemon to go, I'd take 1 over 2 personally. 

And my argument is that a full Dex is inherently better with no tradeoff, and we have previous games that have already proved this. We don't have to think of reasons to think the games would be better with a limited Dex, we have existing reasons to prove the games are better with a full Dex, and existing reasons to prove that a limited Dex doesn't make for more polished games with richer experiences. You've already pointed out the latter with Sw/Sh.

Every existing Pokemon has already taken its dev time. Every single Pokemon that existed on the 3DS games (i.e., Gen 1-7) already has pre-existing HD models and animations that were created for future use. You can find plenty of articles and posts in forums or on Reddit proving this. GameFreak STILL uses them to this day. Go look at something that has been in every single game mainline game, like Lucario. How much has that model and its animations changed? The argument that it would take copious amounts of dev time would apply under normal circumstances, but not in the case of Pokemon. That time was already taken and spent, and until TPC allows GameFreak to redo every model and animation from scratch, that argument holds no water. Heck, GF and Creatures Inc. did MORE work before the 3DS days when every single Pokemon would get new hand-drawn animations for each generation or game.

And again, you've already pointed out a couple of games that didn't benefit from GF's piss-poor excuse for not including a full Dex in Sw/Sh. Those games look like ass, run like ass, and cost $90 before you feel like you've gotten the amount of gameplay you would have gotten in previous games, while STILL not having a full Dex. And Dynamax sucks. So by claiming that including more mon hampers the overall experience, you're carrying GF/TPC's water and allowing them more excuses for less content along with poor optimization.

Yes, Pokemon Stadium exists. I've already pointed out how the animations in it are STILL better than anything GF has done, 25 years later. But Pokemon Stadium wasn't developed by GameFreak. And again, it's around 25 years old, so of course it has a more limited roster and moveset. But that is also a moot point, because you're practically saying that each Pokemon has a unique animation for each one of their moves, when we all know that they don't. That is highly disingenuous. Each mon has like, two animations, maybe three if they are really special; Pikachu has more than that based on it's different costumes and distributions, but it's Pikachu. SSB characters have more taunt animations than most Pokemon have total animations. And Pokemon don't even make contact with each other when doing their attack animations. They usually have one animation for physical attacks, one for special attacks and support moves, and a very simple hurt/faint animation. There is FAR less work in designing Pokemon animations than you're making it sound like. Oh, and did I mention that every single Pokemon that existed on the 3DS games already has pre-existing HD models and animations that were created for future use, like if the devs ever wanted to include them in future HD consoles? Therefore, the work is already done.

You are absolutely entitled to your wants and opinions. However, where I disagree with you is the mistaken belief that including a full Dex means a less polished game. It doesn't. The resources are already there, as is the proof from previous games. We also have proof that a half-ass Dex can still lead to a half-ass game, Sw/Sh. So since we know that the amount of polish, refinement and content in a mainline Pokemon game has nothing to do with whether or not it includes a full Dex, I don't understand why anyone would argue for less available Pokemon, which is absolutely an argument for less content.

There has never been a full Pokemon game with anywhere close to the level of polish that I am talking about, so I'm not sure what game you think managed to do it with a full Dex. It doesn't exist. Again, I am not asking for the same low quality animations to be carried over to the new game. I want new animations that are actually good. 

Oh, so you're asking for a theoretical Pokemon game that GameFreak has never made and has shown less signs of ever making as time marches on. You're asking for something even less realistic than a game with a full roster. While you're at it, go ahead and ask for a Smash Bros. that plays like a 3D arena fighter, or a Star Fox/Metroid/F-Zero crossover with racing and missions that take place in space and on foot.

I agree that a limited Dex doesn't necessarily make a better game. That is why that has never been my argument. However, if we are to speak of the direction of the franchise, I believe that a direction which focuses on building a game with a level of polish that has never been seen in the mainline Pokemon games with a small Dex would create a better experience than a game which keeps offering the same low polish gameplay but with a big Dex.

I would much rather each Pokemon game focus on doing something new (ideally with a limited Dex focusing on new and regional pokemon) than every game just being a messy grab bag of every gimmick they've ever come up with.

A more limited Dex also allows the games to do more with what they have

Sounds like it's your argument. Either way, you're wishing upon a star that cutting content means a more "polished" game (adding more unique animations to Pokemon isn't polish) when that has never been true with this series. Masuda flat out lied about cutting the National Dex in favor of higher quality animations and whatnot, but what happened? Both the new and returning mon in Sw/Sh have two or three animations, just like always.

https://gamerant.com/pokemon-sword-shield-national-dex/

So I was wrong about you towing the company line about less Pokemon meaning better games, but it doesn't change the fact that you're looking for a pot of gold at the end of a rainbow. A game with a full roster of half-ass animated critters is far more realistic and feasible for GF than a game with half a roster full of critters with Sakurai levels of work put in.

I don't know why this is so hard to comprehend. You seem to say it yourself in your post but completely miss the point:

"Go look at something that has been in every single game mainline game, like Lucario. How much has that model and its animations changed? The argument that it would take copious amounts of dev time would apply under normal circumstances, but not in the case of Pokemon. That time was already taken and spent, and until TPC allows GameFreak to redo every model and animation from scratch, that argument holds no water."

Hmmmm, it is almost like you are agreeing with me that the animations are low effort and that it would take a lot of time for GameFreak to redo the models and animations to make them good....

No almost about it. That's the main thing we can agree on. Yeah, I missed your point, but I get it now, and now I'm telling you that it ain't happening. If GF was going to redo the models and animations, why the hell would it still be using those that were made around a decade ago? Why wouldn't GF have done it with Sw/Sh, with Arceus, or with Sc/V? How can GF do it when Pokemon is pretty much CoD where they have a year to pump out a new game from the assembly line from year to year, and the devs barely have time to take a bathroom break between sequels? Why would they even do it when the games are selling as good as ever?

Or, since this miracle Pokemon game you're asking for probably isn't coming before the heat death of the universe, GF could at least put in something a little more realistic than that, which is to include a full Dex in the games, especially since it has all the resources for it already. That's the part you find so hard to comprehend.

"But that is also a moot point, because you're practically saying that each Pokemon has a unique animation for each one of their moves, when we all know that they don't. [...] Each mon has like, two animations, maybe three if they are really special; Pikachu has more than that based on it's different costumes and distributions, but it's Pikachu. SSB characters have more taunt animations than most Pokemon have total animations. And Pokemon don't even make contact with each other when doing their attack animations. They usually have one animation for physical attacks, one for special attacks and support moves, and a very simple hurt/faint animation. "

Yeah, it's almost like I am arguing that the game should have more unique move animations...

Go ahead and argue for Final Fantasy VII Remake to get a Switch port while you're at it.

The transition away from many of the things that make Pokemon games feel low effort and low polish would take a monumental amount of effort with a full Dex to the extent where it is not reasonable to expect these changes if the games maintain a full Dex. If the fanbase continues to demand a full Dex (or even a very large Dex), the game will never get to the point where it has the level of polish that I would like the series to get to. 

Based on what? Your own conjecture? I'm sorry, are you a developer? If so, maybe you can explain to me why GF can keep reusing the same tired ass models it has for around a decade, but it would have to throw everything out the window and rebuild from the ground up to get the miracle game you want. And then when that game's sequel comes out, GF would have to throw all of those assets out and start from scratch again.

That argument makes no sense. It would be far more realistic to say that GF needs to build on what is already there, because there is definitely a foundation. But nope, let's demand that a small studio full of old heads that had to be dragged kicking and screaming into modern gaming development and now has to churn out sequels roughly every two or three years with expansions in between suddenly find the time and inspiration to start all the way from the bottom up. Let's go ahead and ask them to reboot the entire franchise.

And while you're at it, learn the definition of polish.