Superhero RP's can be fun, but I rarely find heroes wrote well-enough for my tastes. I often see characters meant to justify their powers or meant to fit the theme of their powers, and the depth ends there. This isn't universal, and that's another problem, actually. A lot of the time you will have these fantastic characters with great depth. So much that they can reference back key events or even minor influences from their childhood into present day decisions. But, those characters exist within the same setting of the ADHD Speedster that was part of some freak accident because he was running on two days without sleep while interning for his Masters at 22, and literally having no other depth. None. No familial ties, no youth history; he was just a stressed out kid with attention issues and an insanely fast work pace trying to finish uni ASAP. That's being GENEROUS, in fact. So, when you put that in contrast, it just creates this illusion or observation that some heroes are "better" than others even if they aren't more powerful, and that's never healthy, it always causes in-fighting. On top of that, there's always the guy trying to play the de facto hero, like Robin, but after following through with the RP for a while, another character is better liked and less impulsive, and there becomes a huge conflict when they want a new leader.
Superhero RP's, in my experience, can be some of the most fun, but simultaneously they capture the attention of far different kinds of writers at different stages in their life as well as often have VERY strong conflicting themes that just can't easily be dealt with.