People look for excuses to dislike something, which is pretty sad and pathetic to me.
They don't seem to be aware that they can skip catching those Pokemon they don't like. And because they don't like them, their twisted little brain makes them think that no one should like them either.
Because, you know, inanimate objects haven't been present in every gen before, at all. Oh wait, they totally have.
Basically, it's "My nostalgia won't allow me to like anything from the newer games, so I have to try to legitimize my irrational complaints with something that seems like it might make sense to a not-crazy person."