Considering they used to make different sprites for every single Pokémon, for every main game, it feels like a kick in the nuts. On the other hand, there’s about 300 more new Pokémon that exist, and they’re also in 3D. I can see why people are upset, but personally I won’t lose sleep over it.
There's almost no chance for mythical Pokémon like Meloetta. Seems like most people already forgot about most mythical Pokémon sadly, which means they aren't as popular as they used to be, and likely have little chance of ever seeing the light of day again.