>>41339032Ohmori happened.
Technically Ohmori happened since XY, and you can see the cracks with that game as he was a Planning Director for that game, but luckily Masuda was there to tard wrangle him and control his autism.
Unfortunately, Masuda was getting old and he needed someone to act as main director and Ohmori was the only eligible one for that role. That's why Lets Go was Masuda's last directed game.
Ohmori put a huge focus on the railroading, the lack of dungeons or side areas, the focus on story and dialogue dumps, the characters that hog up YOUR spotlight (Zinnia, Lillie, Hop, etc), the lack of postgame, and so on. They're still fine games, just on the lower end of the Pokemon series.