The problem with wanting every Pokémon to have some sort of unique mechanic is that it causes yet another move/ability/item bloat.
my sizzling hot take on item bloat:
"Item Bloat" is only an issue when it comes to evolution (collect these ONE MILLION ITEMS to evolve. when you will get them? who knowsssss~~~~) and organization (which varies game to game and
is extremely lacking). Yeah they could remove a number of battle items that only serve niche uses but them being there doesn't actually hurt anything either. Basically there being like 17 kind of usless very niche battle items isn't really an issue, but 17 Silvally Memories is an issue becaues they'res omething you're expected to swap in & out of and they keep getting put into the middle and then the end of a bag when they could be consolidated into one key item ala the Rotom Catalog. Even if there were 100 less items that's still going to be an issue. Likewise have one million type boosting items or legendary held items as you want, I just want them in separate bag pockets so I can shuffle them in/out while looking for my trade evolution items. In contrast I see very few people complain (& yes im sure i'll get a litany of people going
actually i dont like those but you cant deny you dont see as much complaints about them!) about the various vendor trash items and full heal expys and I think a lot of that is because they have their own, much smaller, sections in the bag.
"Ability Bloat" is, likewise, not an issue at all. Again there's some worthless ones we could probably excise (light metal, heavy metal...) but its just...there being a bunch of them doesnt matter to anything. Implementation is likely fairly static at this point and while it is silly that there's multiple abilities that do the exact same thing thats a separate issue. You're not swaping abilities in & out on a whim, pokemon only have at most 3 and they are pre-set.
I would be surprised if we ever get a proper "abilitexit" or "itexit", to put it another way. There were some of both that got left behind but that's more due to their attached pokemon not being around (like the razor fang). And there's a bunch of new stuff specific to Galar that'll obviously not return. But I mean
completely removed, long standing items gone entirely, purposefully like moves were and with no plans to ever bring them back. Even megas will probably come back
eventually bringing their stones with them, but something like comet punch probably never will.
"Move Bloat" I can at least see being an issue again at somepoint. Move culling was a thing that happened this generation, after all. And moves, unlike items & abilities, likely require far more effort to do.
But also I think if they really cared about this, and it wasn't just caused by
other issues compounding on top of everything, they probably wouldn't have made another like what 40 signature moves and then add another like 30 moves in DLC. I also think they would have cut
way more moves in the first place, to clear the deck for future plans.
Basically the answer here should be
remove more moves and
create fewer moves. But they did neither despite it being a good a point as any to make that decision, and likely would have been a far less harsh decision that dexit was to begin with.
Actually having written it out like that, the move decision might've partially (gen 7 did a lot of signature moves too) been made with dexit in mind? If there's more signature moves than if those Pokemon
don't show up they can punt having to make new animations for a while. I guess we'll see what happens in gen 9, since I imagine they'll just reuse all these animations for whatever is left in gen 8.