Diversity

Comic books have been the most interesting representative for our society. In those, we can see the political, economical, social allegories. Our heroes and villains have been created just like our desires. Good looking, well-educated heroes and ugly and always rude villains. That is the most stereotypical featuring of our comic book characters. When we think about Captain America; we think about a white, good looking and Nazi ass-kicker guy. Or when we say Thor; funny talking, British accent and the destruction are the first things we think about. We have always a thought about what a superhero or a villain should be about. All those years, the comic book creators have been created the characters just like we wanted.
Even accepting some changes was difficult because we always see the characters with some secure features and if we think we are losing the features, we publicly will be against those changes because people don't like the changes. Thus, they fear that they are losing the control. You may think that it is too much about a comic book but you may look around. If something so-called cliche is changing or is about to change, public will be against the changing. The reasons may be in varieties but the point is the losing the control. Because we don't know if “the new” is good or bad, reasonable to not. Because we don't know the purpose exactly.
When we think about Captain America for example, the reason about it because there was a huge changing of it, we always see the white, blonde, “perfect” guy and he is an unquestionable man in the world about fighting with the evil. Marvel company made a huge decision about him and long story short, we had a new Captain America and this time our character was Sam Wilson a.k.a. Falcon. Afro-American and not so popular. Captain America wasn't the only character Marvel has changed. Ms. Marvel has become a young Muslim girl, Thor has become Jane Foster, Thor’s love interest, Hulk has become an Asian kid and so on.
It must be a good reason for all these changing for example, marketing or story development. We can see MCU -Marvel Cinematic Universe- has been the highest grossing film franchise and the age gap for the target audience is teenagers. Some people don't like the idea for changing because they think it would affect the target audience but some people are happy about it. The reasons can be different from the money issue to the lack of diversity of the characters.
Before Marvel, DC has made a huge changing. Even not just one. Marvel can be the most fan-based favourite comic book publisher in the world but DC owns the stage. About the backstories, characters’ history DC has definitely more varieties than Marvel Comics. But why did DC make four Flash characters or more than four Green Lanterns? The ratings or the popularity can be answers or the competition. When we take a look at the Flash; there was first Jay Garrick for almost 10 years he was the Flash, then suddenly Barry Allen took his place then Wally West has been replaced and he was the main Flash for almost 25 years. Then Barry Allen returned. And I can remind you that with all the replacements, people were against them. So, we can say that we can make people happy for sure because they are going to be against the change all the time. We have to remember that Robin a.k.a. Jason Todd has been killed by the people via telephone texts during 80’s but when he returned to the storyline people were happy about it and now his alter ego, Red Hood is one of the favourite characters.
The result for those examples can be explained with the fear, I think.