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3D Pokemon was the beginning of the end, but it's a mistake to say that Game Freak stopped caring entirely. SM absolutely had passion put into it. The island trials, the culture of Alola, and the story surrounding the Aether family were all very thoughtful. It's just not a very good Pokemon game. It's trying way too hard to be a story driven JRPG for kids, and completely misses the draw of the series. It had plenty of effort, but not in the places that Pokemon fans actually care about.
XY also had tons of effort put into it. Mostly with respect to the gameplay and systems of the series. As much as people whine about MUH POSTGAME, XY still generated a-lot of activity in it's first years thanks to huge advancements in PvP, Training mechanics, Dex filling, and customization. Pokemon exploded as a social experience to begin with, and XY perfected it. Not to mention bringing every Pokemon into 3D with super polished models and unique animations for all of them. It also addressed some of the smaller problems with BW, like the lack of Triple/Rotation Battles, the limited Pokemon roster, the removal of berry farming, or the VS Recorder only saving one fucking battle per save file. XY was a step forward in many ways.
The problem I think, which is now being magnified by SwSh, is Game Freak's proficiency as a developer in the modern world. It's not coincidence that 3DS is where many fans started to sense a decline. They weren't ready to make the jump. Other games on the system run better, and are more technically impressive. And on top of that, they have to worry about modern kids and casual mobile gamers, so everything has to be spoonfed and easy. Hence the gradual loss of content.
It sucks, but it's easier to make peace with these games than fucking SwSh. This has been nothing but empty promises and bad PR.