I love The Muppets but I think Superheroes are a little more versatile in the kind of approaches/material they can deal with. Like from their inception Superheroes are these outlandish figures who tackle real world issues like crime, social issues, gender equality, etc.
Both share the issue of sometimes needing to use still images to carry the story to give the animators a break but at least the movies have never done something on par with that video game/Wally fever dream sequence...