Super Mario Sunshine: What went wrong?

Infendo

Released in 2002 for GameCube, Super Mario Sunshine was by no means a bad game. But it wasn’t great either — far from the caliber of  other Mario games. Anyone who says otherwise needs to take their Mario Goggles off. (Miyamoto is capable of releasing at least one dud, right? Two if you count Wii Music.)

Whatever your opinion of the game, I think it’s safe to say Sunshine is definitely not the best Mario game. So what did the others have that this game didn’t? What was wrong with Sunshine, noting everything that was right about other Super Marios?

Let’s hear it, Infendo. I know you have the answer.