I played both in my childhood, and I don’t think I’ve ever returned to Tooie after I beat it first time. It’s a good game, but doesn’t have that same lasting appeal as the first game.
You touched a bit on the why: the game is too ambitious. The levels are too massive and too intertwined. Smaller isolated levels fit the collectathon format better.
I remember having lots of fun with the multiplayer though, so that’s a bonus.
If you want to continue the collectathon journey you should try out Donkey Kong 64. It’s also a game that falls under its own ambitions, but in different ways. Still a good game, but nothing beats Kazooie.