Every new mainline game makes me miss the BW formula even more when it comes to limiting players to new Pokemon specific to a certain region at least to some point in the story.
Getting a brand new Pokedex full of new shit to learn and get familiar with was the peak of immersion and best way to keep the spirit of discovery in games.
I'm honestly displeased with facing trainers in new regions and see them using a single new Pokemon at best.