Originally Posted by
Mister Mets
It seems that Marvel is trying to delay the bursting of the superhero film bubble by making sure that many of the films can count as work from other genres. Thor is high fantasy. Winter Solider was a political thriller.
Guardians of the Galaxy is a space opera. Marvel didn't have a film franchise that fit that category, which includes some monster hits (the Star Wars/ Star Trek films, Avatar.)
Doctor Strange is contemporary fantasy. That genre has also done well.
One issue with Black Panther and Black Widow films is that there would be genre overlap with the Captain America films.
A unique problem with Carol Danvers is that her origin is tied to a male superhero with more acclaimed stories. There is no Carol Danvers solo story with the critical reputation of Jim Starlin's Captain Marvel run, especially the Death of Captain Marvel. If I was advising Marvel what to do with that series, I'd suggest making a film about Mar-Vell that ends with his death (something that hasn't been done with superhero films) and Carol Danvers getting superpowers/ becoming a potential Avenger.
The characters were created in racist/ sexist/ homophobic times. But this has left them with the prime mover advantage. So film writers have more material to use with Iron Man, Captain America, Thor and the Hulk than with other potential leads.