I'd like to see the option for 1:1 sword combat restored to Zelda. Skyward Sword remains far and away the Zelda game with the best combat in my opinion.
It's time for a real shakeup to the Splatoon formula. Not sure what they could do differently, but 3 games being so similar is enough.
Xenoblade should have another game that's more like XCX with the fully open world and especially the flying mech suits. The hardware for the Switch 2 should make that as mind-blowing as the original XCX was in 2015.
Paper Mario should go back to its original formula or even do a modern take on the Super Paper Mario formula.
Donkey Kong needs to go 3D like Kirby recently did, but with a more linear and focused level design than DK64.
'Switch Sports' needs to go back to Wuhu Island.
Mario Kart needs to bring back the single player missions from the DS game.