Ah, okay. Funny enough, you're not the only person to have complained about Shake It being disappointing from a game design perspective.
Yeah, I think I've rambled about it extensively on another topic, but in case people haven't read it:
The thing that bothered me about the level design was that it always felt like the game was trying to troll me.
"Oh, you chose the bottom path?
WELL GUESS WHAT, ASSHOLE, YOU WERE SUPPOSED TO TAKE THE TOP PATH AND NOW YOU CAN'T GET BACK SO FUCK YOU! PLAY THIS SLOW, WAY TOO LONG AND NOT VERY FUN MINIGAME-LEVEL AGAIN!"
I mean just tell me how many times you dropped down a hole, only to land at the bottom and learn that you should've done a ground pound from the top but there was no way of knowing that before so now you gotta play it again if you want the treasure.
You might think, "Ok, then I'll just always do a ground pound when I fall down a hole, right?" No, I'm pretty sure, (tho I can't prove it right now, since I don't remember the exact location) that there's one place where you can miss the treasure if you DO perform a ground pound.
In general there are a ton of things that you can easily mess up if it's your first time playing and then can never retry unless you replay the level.
It's stuff like that that just isn't fun. Kirby was guilty of stuff like that for a long time, fortunately they have dropped that bullshit in recent games and all the puzzles are fair.
There's also the stupid motion control segments with the vehicles but that's technically not part of the level design.
There are probably more subtle aspects that make the levels less fun to play through but this is the one that I always remember hating.