High difficulty is probably the most common conflicting game design aspect.  It's a great motivator, until it becomes too much for you and you get too frustrated to enjoy a game.  It's a learning experience and it depends on the person entirely.  If you can keep up at it, then it can give you at the very least greater willpower and a stronger resolve....even in life because you're doing something you enjoy to begin with in playing video games.

My person most conflicting one would probaby be missables in RPGs.  Especially if you have to be at a certain place at a certain time to get that thing, whatever it is: item, power, person, status buff, whatever.  I can understand that it adds to the replayability, but it can be infuriating to know you have to start a whole new game over again to have a chance to get it.  It's exciting however in that it requires you pay attention to every little thing and talk to every person in an attempt to get it.  It makes everything you do that much more useful and a motivator in an RPG.  It's also monotonous however...to keep checking everything.  This is where making a game have a specific art style for every area useful as visually memorable, including all the characters you meet, which imo is even more important.  So if that's done right, then I am completely ok with missable items.  If every NPC in the game looks too similar and the places you go repeat too often in visual prowess or the NPCs look too much alike (adding on a larger world makes this even worse than if it were linear) the process of discovering things becomes monotonous by default.

For me it's hard to come by items in the form of ammo or perishable powerful items. While it is fun when you find them I tend to never use them. I always save them for later which negates the fun of finding them. I ended The last of us maxed out in items, ended Fallout 4 with a ridiculous amount of powerful yet never used weapons and ammo. Which is also the result of another conflicting design choice. Weight limits. It adds a bit of choice of what you can carry at any time, but it also limits experimentation and fun. Just let me take all the weapons with me.

These things can be done right. For example hard to find items that unlock abilities like the spells and potions in The Witcher 3. Once you have it, use it as many times as you want. Only use weight limits for equipped armor and weapons as in the souls series, no limit on inventory.

You just reminded me that you can miss a complete optional yet lenghty and rewarding dungeon area which has also ties to the main story (and some funny easter eggs altogether) in Tales of Vesperia if you don't happen to travel all the way to a certain part you've already visited in the world, in a crucial plot story moment, despite what common sense might tell you. It's baffling, and there's no second chances; proceeding forward the story and coming back won't trigger it. So I can say I totally relate to that one.

I'd say people with Plot Armor in these "your choices will affect the outcome of the story" kind of games is what I find most conflicting. I know there's got to be some kind of anchor so that the story doesn't get extremely weird because the plot character isn't where he or she should be, but sometimes it just don't make sense, and I don't understand why the devs didn't think of a workaround of it. The most notable examples? Ethan Mars and Scott Shelby in Heavy Rain or Mike in Until Dawn. There's entire subtplots that rely on the character being alive, and the game will do whatever it can to achieve that, thus giving the player the biggest illusion of choice they can. As a result, there are scenes that lack any kind of proper resolve or logic. Try getting Ethan killed during the Butterfly trial, for example (Heavy Rain spoiler), or expose Mike to any danger you can prior to the final cabin sequence (Until Dawn spoiler). They're simply unkillable, and the game will conveniently skip the chapter altogether and just give a bullshit excuse (or just don't explain anything at all) and the game carries on like normal.

"It's a great motivator, until it becomes too much for you and you get too frustrated to enjoy a game."

That's literally never happened to me.

Happened to me a number of times, hell some old games that don't do difficulty options have kept me from touching a few games ever again. I'm not the kind of guy who only plays games to have my knuckles shattered though.

Give it time. Wait until you have 2 kids, a busy job and can't keep your eyes open anymore past 10 pm.

Actually it happened the other way around to me. I quit Jack and Dexter 2 when it came out, too frustrating. Finished it in the remaster. No more crazy working after hours anymore. Anyway I don't really care for challenges anymore and simply set a lower difficulty before it can become annoying. Most games aren't worth playing over and over until you get it anymore.

I think most games are easy enough to learn the mechanics through experience. Nobody who enjoys "difficult games" likes them because they're difficult. We like them because the gameplay is nuanced in a way that easier games can't ever be.

It's the equivalent to enjoying Shakespeare. Nobody who likes Shakespeare likes it because it's "difficult to read." They like it because he's really good with words. You just need to be an extremely experienced reader to understand why. Same with difficult games. It's not "knuckle shatteringly hard" when you've reached a certain level of gaming skill, the same way Shakespeare isn't "impossible to decipher" when you're a good reader.

I'll never play games like that. That's like skimming through a book or fast forwarding through a movie because you "don't have time" to experience it thouroughly. I don't play games just to finish them.

I play games to experience the world, not to take a skill test.
It's not comparable to fast forwarding a movie, it's watching the movie without constantly rewinding.

It depends on the game though. Racing games are my skill test. lvl 120 +49 in DC, #720 on the world leaderboard and still climbing.

But there are people who enjoy the actual difficulty, the challenge of how hard a game can be, just like those in real life who look at an impossible challenge and get all giddy and happy because they want to take it head on, there are others in life who just don't want that sort of deal up front and center and it happens with games. You can still learn how a game works and still get put fof by it's brutal difficulty, I can figure out how a game works but that doesn't mean there isn't a fault with it's difficulty.