They really are.
They have been, actually.
There was, last year, some Natasha/T’challa stuff where after Black fans were like “mm… no” they were accused of actually hating interracial relationships. I saw (and screenshot) the opening line of a story where T’challa and Tony get married and, after T’challa dies, Tony takes the throne. (This fic,as far as I can tell, came out AFTER the film so… they knew better.)
I’ve seen “white consort of Wakanda” stories as well where the white character may not end up running the country, but still gains some serious power in Wakanda that they literally have NO business having.