Here is the list of things that I dislike from the switch of gen 6 to gen 7:
>the removal of badges and changing them to stamps feels less rewarding
>the removal of the national dex makes the game feel incomplete
>being several islands instead of one consistant island and makes flying needlessly complex
>with the addition of ride pokemon it makes the areas feel restricted
>the z-moves only feel good for the exclusive ones (like pikachu or mimikyu)
>they should have of added new megas along with the addition of z-moves
>the festival plaza is a needlessly complex way to interact with friends (the PSS was great)
>the pokemon pelago was a joke and has no purpose what-so-ever
>the ice stone to evolve alolan ninetails/sandslash was pointless (could've just level up in snowy area)
>the region variants should have of spanned all of the first 4 gens rather than just gen 1
>the removal of the hall of fame pc as well as your own pc was bad

But here are somethings that I did like from the switch of gen 6 to gen 7:
>the ride pokemon do make it easier on your team to not have HM slaves
>the day/night mechanic works a lot better than it did in gen 6 as well as gen 5 and gen 4
>the caught pokemon party replacement mechanic is usefull
>the zygard cores you could collect did add some level (not much) to my experience

all in all i do hope they fix what they have done to pokemon in gen 7 and fix it in gen 8.