I don't normally think about the controls of a game when I'm playing, especially if the layout works well, so I often forget exactly which buttons/commands perform which actions because I just respond, I don't think "press A" every time I make Mario jump (is it A?). The only reason I remember Luigi's Mansion using the analogue of the shoulder buttons is because it was the first game I played that used them, so it sticks out in my mind as being a first experience. Notice how I didn't mention what the shoulder buttons actually do in the game; I don't remember that detail, but I do know they were used.
Super Mario Sunshine is a plenty fine Mario game, the problem is that some fans are too narrow-minded as to what makes a Mario game. My issue with the game has nothing to do with the water pack, it's that the game was clearly rushed out the door, and so there are way too many filler shines, most notably all those blue coins. As much as I enjoy the game, I've never collected all 120 shines because it simply isn't fun to do so, I'll get about 80 and then be done with that playthrough.
It was a good game except for the fact the water thing was strapped to Mario's back the whole game. If it had just been a powerup thing that you use at certain times and then unequipped it and returned to a traditional Mario platformer experience then it would have been a much better game.
You mean like all of those sections where the water pack is stripped from you? Coincidentally, most critics considered those to be the best parts of the game, which is likely because, at the time, they were the closest a 3D Mario game has come to being like the NES games in 3D. It's my guess that the sections partially inspired Super Mario Galaxy, which may have to do with the positive critical response or the ideas that sparked from creating them or maybe even both.