The only MCU character that was somewhat known to the general public prior to MCU being a thing is Hulk, and his solo movie did the worst of them all. So all this "Marvel doesn't have a popular female character" is empty talk. Where there's will there's a way, but there obviously was no will in the MCU, because for a long time they have made little to no effort to stray away from the straight white male protagonist.
Compare that to DCEU, which started later, but where we already have Wonder Woman, Suicide Squad which was fronted by a black man and a woman (with the rest of the cast being even more diverse), and even Aquaman and the Flash, who are in the comics traditionally depicted as blonde white dudes, were cast as a Native Hawaiian and a Jewish queer guy...
I really hope that Black Panther and Captain Marvel turn out great and do well, but both are long overdue, and for all that Kevin Feige now talks about how "it doesn't matter if the movie is good", he just sounds like a giant hypocrite, because it's obvious the company policy was not to test that theory out.