Now I haven't played through Let's Go entirely yet (I just beat Lt. Surge) but I believe the game itself was made for the exact purpose of bringing in new kid players who have had yet to experience Pokemon, and what better way to do that than to recreate the first generation (again) with a catching mechanic rather than the battling that us players are so used to. It would have been nice to have a challenge, or at the very least have a hard mode, but oh well. The future will tell if that marketing strategy ends up paying off.
I think it's safe and sad to say that Pokemon has definitely hit and gone past it's golden point though. Now it's just a waiting game until the game itself finally dies off. The only thing I still want out of Game Freak at this point are Gen 4 remakes. As said by you, I'd much rather play Reborn or another mature/ difficult not Pokemon, Pokemon game nowadays. It's the only way it stays fresh to me. And Nintendo is too much of a kid-friendly company to do what would be necessary in order to fully revive the game for a lot of players. Of course, this is all just my opinion.