Marvel tried; they truly did.
Ava Duvernay was a hot commodity for awhile in Tinseltown, mainly due to her backing by Oprah, and they gave her the helm for BLACK PANTHER. The film is about a black superhero, and not just a white superhero the H3L cast as black in an attempt to demonstrate diversity. Well, Duvernay has walked from the project, claiming the all inclusive "creative differences". My sources say Marvel kicked her off the project for basic incompetence. Remember, this is the woman who distorted history badly in SELMA to tell a politically correct narrative. Apparently, she attempted a similar approach, that Marvel simply would not consent to.
This woman has had the opportunities of a lifetime, and so far, she's blown everyone of them.