PWT isn't that great

Yes, it is ;)

It's one of my favorite features from any pokemon game along with the Battle Frontier and I love that you can battle the gym leaders and champions from EVERY region, which makes it one of the best things to ever happen in a pokémon game. I would love to see it back in the future.

The Battle Tree is similar and fuctions more like from Colosseum or Gale of Darkness' Battle Mountain

I haven't beaten the game yet, but I read this review anyway since the story is pretty hollow and uninteresting so far thus I don't really care if it get's spoiled. I'll be fair and not rag on it until I've fully beaten it, but besides story stuff I agree with most everything else you've said. I love actually having all 6 slots available now that I don't need HM slaves, but I woulda loved having more new Pokemon to fill those slots with. Though imo practically all of the ones we did get are great to amazing, perhaps they just went for quality over quanity this time, and if so then I'd be fine with this as long as future gens have just as great a line-up of Pokemon.

I'm only on the second island, so my thoughts might change, but so far I've found the callbacks to previous gens to be less one-sided than in X/Y. You'll see Snubulls in police stations, a farm of Miltanks, and Gen 5 Pokemon everywhere (at least I assume so, since I skipped that gen, and the majority of the pokemon I see I don't recognize). Giratina even gets a random mention in a laboratory area connected to the main story. 

The ride pokemon actions are completely independent from battle moves, and so far I haven't seen any HMs. Rock Smash is a regular move, and I think that was an HM for a while, but it's purely for combat.

Nope to the first two questions, yep to the last. I taught my Oricorio Fly to try it but there's no option for it to use Fly in the field. There's never any reason to want to use your own Pokemon for this so it's a non-issue.

Less than X/Y? Mega evolutions and Fairy-type applied to all gens, while Alola forms are Gen 1 only.

I'd compare Mega Evolutions more to Z-moves, which literally are applicable to everyone, assuming they have a move of a certain typing. As I recall, a disproportionate amount of the Mega Evolutions were gen 1 anyway...though maybe there were a ton of others I weren't aware of. This game definitely doesn't give you a 2nd starter like X/Y (even if I wouldn't mind having another Charmander).

I haven't seen as many Alola forms as I was expecting honestly...so not sure if that's a real issue or not yet.

 X/Y was no more nostalgia-dependent than any previous gen. This one took a bit too far. Alolan forms are only of Gen1 pokemon. Your character comes from Kanto. You get to battle Blue and Red. Theres a character that's named Oak, thats pofessor Oak's cousin and look exactly like him with a tan!!! Like wtf

I don't think even half the Megas were Gen 1, such as Lucario, Scizor, Salamence, Mawile, Garchomp, Houndoom, Gardevoir, Abomasnow, Absol, Blaziken, and probably more. The only Gen 1s I can recall are the starters, Mewtwo, Khangaskan, Alakazam, and Areodactyl, but there's probably a couple more. Getting a second starter isn't as impactful a new forms, as the former can be ignored while the latter cannot as even if you don't use Alola forms yourself they can be used against you, changing up the game eitherway.

None of this is an issue really, atleast not to me (yet), but I definitely woulda preffered it if Alola forms were not Gen 1 only.