The game sales say otherwise.

If you mean the quality of the game, that is of course up for debate. But what's interesting is despite Pokemon games on Switch usually looking like upscaled Wii games, they're selling like crazy. 

It's possible that Pokemon sales dip massively on NG (Next-Gen) due to oversaturation or technical problems/gameplay aspects, but I'm sure they would at least still be profitable. 

yes pokemon did grow during the switch era

It definitely grew on the Switch but not as much as other series. Zelda, 3D Mario, Animal Crossing and other series all broke their personal bests, some besting their recording by double the sales or more.

I've always felt that if Gamefreak put a bit more work on the mainline games that they would have an unstoppable force. They managed to sell 25m+ for a game that looks like an upscaled 3DS game

Yes I would say with the popularity of social media. But not with younger people but mainly with old fans discovering there childhood again.