I can definitely see both sides of the argument here. I can't fault people for being mad that its going to take over a decade and 20 movies before we see a solo female hero.
But at the same time, from a purely money making standpoint, i can't find much fault with the decision making at Marvel. people like to say 'how come its taken so long to get a non-white male movie on?' Fair question. But i look back at Phase 1 and 2 and i cant point to one movie that should have been taken off the docket in favor of a black widow/Black panther/Captain Marvel movie. The only one is Ant Man, and frankly that movie was made only because of Edgar Wright and the fact that they had already sunk a bunch of money into it since 2008.
Iron Man, Thor and cap will always get sequels as long as the stars are game. They're confirmed moneymakers. And Marvel has made it a point of releasing sequels within a 3 yr window which once again makes sense.
Its very frustrating but Marvel will always work around that bottom line. Characters will be prioritized by how much money they can pull in for better or for worse. Ant Man is going to make 500 mill, that immediately pushes that franchise ahead of BP, Cap Marvel, Strange, Widow etc in terms of importance to the studio
As a fan, i want Marvel Studios to be progressive and shatter barriers when it comes to diversity and representation in film. And its within their power to do so, probably more than any other franchise in hollywood save for Star Wars. But as a businessman, i get their way of thinking. I don't like it, but i get it.