Sunshine was rushed and it shows. I find that there are plenty of fun levels, but there are also a larger percentage of levels that are not fun than in any other Mario game. The worst part is that unlike 64 or Galaxy you can't skip any levels you don't like and just get the minimum number of shines. You have to get the first 7 shines in each world without exception and you can't even do them out of order like in 64.
The problems I had in terms of control were primarily camera based. Whenever Mario was on a narrow platform I could never move more than a snail's pace because no matter what the camera would not line up behind Mario on the platform and so Mario would want to run off the platform, and that's before such masterpieces as the ferris wheel level where you can't see crap. Wider areas where the camera could afford to be pulled back weren't a problem and Fludd often took away the need for precision, but those areas where precision was needed were a nightmare.
The game needed another 6 months to iron out the kinks in 2002, and one of the disappointments of the 2020 rerelease is that they didn't fix any of the 18-year-old issues with the game.