This is the equivalent of making a Captain America poster, and imposing a picture of him over the entirety of North America, Canada and Mexico included. Seriously, do Hollywood filmmakers seriously think that Africa is a single country? I've seen African immigrants from Nigeria, Somalia, and Egypt and they were all vastly different in their culture and appearance. One of the main reasons parts of Africa are in bad shape is because of incessant tribal warfare between disparate groups. They'd be insulted if you tried to lump them in together with their rival groups, the same way Chinese would be upset if you tried to lump them in with the Japanese.
Liberals really DO believe that "blackness" is a uniform, monolithic state of being that all people with dark skin share - that's why their Identity Politics crap is idiotic and unnuanced. You can't slap all of the people who are descended from an entire friggin' continent with a single label and expect it to explain their place in the universe. And as far as the Black Panther movie is concerned, you might as well just scrap the name "Wakanda" and say that it takes place in "Africaland." Because that is exactly what the Hollywood execs and writers who made this movie think.