there really is a pretty sharp divide in approach between the “2D” (Gen I–V) and “3D” (Gen VI–IX) pokémon games and this really illustrates it

Gens VI and beyond have really focused increasingly on pokémon ecology and how pokémon might fill different ecological niches in different regions, with larger pokédexes, more reuse of old pokémon, new regional forms, and pokédex entries which emphasize relationships between species of different generations

i think this is generally pretty cool but it also means more of an emphasis on catching (which was disadvantageous prior to Gen VI as it didn't give you experience) as completing the (even regional) pokédex has become a much more arduous task

simultaneously there has been a reduction in the importance of other aspects of the overworld as HMs have been removed and overworld puzzles have been made simpler; you don't explore to get special TMs or items, you explore to catch pokémon