Nobody said it was easy.
It's not easy to create an original character, but it's also not easy to move an existing one from one medium to another.
And I totally agree that the lack of diversity is already affecting the growth of the MCU, that's where this conversation started. They're getting criticism for decisions made in 'Dr Strange' and 'Iron Fist' and that's going to continue unless they change their approach.
Now, do they care enough to do that? Is it a big enough problem that Disney will insist they do better?
Disney animation worked hard on 'Moana' and got a lot more praise than criticism for the end result, plus it was a hit. If Marvel puts the same kind of effort in they should get the same kind of result.
So, totally agree, it's not easy. It is possible though.