I honestly believe they are doing it because they know they can get away with it. I don't think they are trying to make a bad product but I do think they know they don't have to give it their all. I honestly don't have much faith in Pokemon right now. They have done a lot to hurt me this year.
I think it's kinda been that case since Sun and Moon. Gen 5 felt like the last time they really put ALL their effort into their games and made something absolutely fantastic. The stretch from Platinum to BW2 is what I consider Pokemon's golden age. While I loved gen 6, I could understand its faults due to them getting their footing into 3DS technology. They were still great games anyways, XY is in my top 5 despite the lackluster postgame. But where gen 6 faltered, it made up for in a lot of really cool features, like soaring, the best online system the series has had, Megas, etc. They weren't perfect but they were pretty solid entries. (And gen 6 had some of my favorite designs in the series anyways)
Then Sun and Moon threw it all away. It just felt like for every step forward gen 6 took, gen 7 took 2 steps back. Festival Plaza? Horrible. Alola? Lackluster region for over half of it (the third island is a jumbled mess). We got a more solid way of moving in 3D, but Sun and Moon, as a WHOLE just felt so much lesser. And then came Ultra, and while sure, it fixed a few things, it was NOT substantial enough to be considered a good sister version. It didn't fix SM's issues like Platinum did to DP, or Emerald and Crystal to their versions, and it didn't build on what was already amazing like BW2 did.
I think SM's faults are in part because of Ohmori's lack of either experience or talent as a director (I'm leaning more toward experience, but if he keeps proving himself wrong that part of me that thinks he might just be bad could come to fruition), and because GF just is starting to put less and less effort in their games, like you said. SwSh is taking that but going even WORSE with it. At least people are finally making a big deal out of it, as they should. I hope one day they take a note from the devs of the new Animal Crossing, or Luigi's Mansion. They're getting a lot of good press because of how healthy their development cycle is on those games, and I think people are noticing, and its drumming up excitement for the games.
But as it stands, GF knows they'll sell Pokemon. They know people will eat it up, and there's not much to be done. I just hope people continue to push for better games in the series. We're going to a
sixty dollar price tag, and yet we're getting less than even the most lackluster of $40 Pokemon games. There's something to be said for that. I could forgive XY for being rough around the edges, but with that game at least I could have all my Pokemon, and it was their FIRST game on the 3DS. This is their second on the switch, yet it's somehow even worse in quality than Let's Go.
The solution is so simple, just delay the game, or hire more staff. But nope, gotta hit that deadline. It just puts GF in a bad spotlight, especially when you have so many other releases coming out, like Luigi's Mansion, AC, or even that new Fire Emblem that just came out looking better than it. They're more than capable of making really solid games, but they need to get their act together. It'd probably make them more money they did, anyways.