One think that i dislike a lot of american animation is that everything is done to last as much as it can. In Japan most of things have a small set of episodes settled for it an then the studio moves on to other proyects very fast.
So things will always keep fresh. ¿How many series with females main characters there have been only in this year?. And that will not suppose any problem to do another bunch of different ones the next year who doesn,t have anything to do with the ones of this year.
Also in Marvel case. When was the last time that they did a single chacater focused animation?. They always choose a demographic or a theme and paint every character with the same brush. Its a cartoon with the avengers for boys If it,s spiderman they will put a lot spider-character and the LOVE SCIENCE. If they are girls they will paint everything with a pink/tumblr based idea.
If where Japan you will get some chances of each character getting its own show.
Fuck it even if they were bad I will always admire what Madhouse tried to do in 2011, 4 series different staff and 12 episodes, one single character each one with a clear story arc and when is over is over. I wish that marvel will have the actual balls to do at the very least a single series with that actitude once in a while.
Having Marvel doing a short lenght animation focused in a single character seems imposible nowadays.