Thanks for this thread, I've had all of this on my mind since the announcement.
I've played all the main series Pokemon games (minus AROS and Ultra S/M), but couldn't finish X/Y or S/M. I'm not sure why. I thought maybe I was just getting older and couldn't dig it anymore, but I bought and played through Yellow on my 3DS for the 20th anniversary and loved it.
I think there is just too much now and I'm not sure what to do with these games. Too many Pokemon, too many mechanics, and a stale predictable story.
I hope this game both simultaneously returns to basics, and then builds in a new direction from there. I think I'm more excited for "Let's Go" than I have been about any Pokemon game since Black/White (which wasn't my favorite). Return to Kanto, return to the original Pokemon, but all new ways of doing the old things, rather than just piling on new things. My only fear is the interface with Pokemon Go. Haven't touched that game yet, and am worried that it will be a requirement for this game.
I'm still skeptical and will wait for reviews and such, but I think this might be the game that brings me back.