Imo:
- Boring levels (Noki Bay especially). A lot of them feel the same.
- Boring objectives (brushing teeth, cleaning graffiti, chasing Shadow Mario, leaf/canoe physics, blue coins). Literally the plot is that you're falsely convicted and they force you to become a narc.
- Boring main mechanic (FLUDD)
- Boring bosses (Petey Piranha, final boss)
- Every level is a beach whereas other Mario games you'd get different themes
- With very few exceptions, having to collect the shines in order in a level, instead of getting to explore and stumble across them. This excludes the sequence breaking that speedrunners do because 99% of players aren't going to do that
- No way to tell if you've collected all the blue coins in an area, or what mission they're in
- I don't even think the water looked *that* nice given Star Fox Adventures released around the same time and has it beat. Like it's fine for beach water but gets a bit old after the 6th world with it.
- Jak and Daxter did the, 'one island collectathon where you can see the levels in the distance and travel to them' a year earlier. It does it better because it literally is *one world* without loading zones and you just walk to the place. It also has different level themes.