Not so sure being partially owned by Nintendo is Pokémons problem. It's clear that gamefreak themselves is the biggest problem, and if gamefreak was suddenly third party, most all of the problems would still be there imo. Perhaps if they were fully owned by nintendo, nintendo would push harder for better quality games, or maybe not. Who could say for sure. Either way I 100% agree that the games are not up to the quality they should be.
They need a major art style overhaul, the switch to 3D has left it looking incredibly bland and generic. Perhaps an unpopular opinion, but the 3rd, and 4th gen games were very visually dull as well. The animations are also incredibly bad and have been for a really long time, the N64 animations still beat the current games in the animation department. A character/creature design overhaul, it's always been hit or miss since gen 1. I know they can't all be great, but damn some of them never should have even left the sketchbooks. They need to hire writers, have actually story and characters. The writing is some of the most bland and boring drivel ever. Honestly insulting how bad it is, a kindergartener could write more interesting characters and story.
A gameplay step up would be nice, honestly, I'd love to see them switch to pure double battles like the gamecube games. I think that gamefreak even realizes the gameplay isn't quite up to par, and that's why each gen they switch it up with gimmicks like Mega evo, Z moves, and the gigamax bs. But honestly, I don't think those gimmicks are the right way to fix that issue. Doesn't help that instead of sticking with their best gimmick, mega evos, they then switched it out for even worse gimmicks.
Add difficulty back in, no clue why it was only included in a single set of games. They should also make the game more rewarding to play. Give special rewards for players who complete tougher tasks like collecting them all. I want to feel rewarded when I beat the Elite 4, and other legendary trainers. Also, handing out legendary pokemon, or forcing the player to capture them to continue the game is really lame too. Like yeah no one wants to miss a legendary, and you'd just save scum to get it, but it makes it feel fake, and like there isn't a reward if they force the legendary into the player's hand.
Never played Temtem, and not interested though, so no clue how well it compares to pokemon. But any competition to make gamefreak sweat a little is a good thing imo.