The idea they can't decide who their flagship characters are is just not true, the decision to have Captain America and Iron Man be the faces of the MCU was something done before the movies even hit theaters.
Same with Chadwick Boseman as Black Panther, it was something very clearly decided before that movie had proved to be a success, it's why a large portion of Infinity War took place in Wakanda.
Also frankly using the Marvels doesn't really mean anything, when we look at all thr circumstances surrounding the movie, and look at the fact the first Captain Marvel was a huge success.
A couple of years ago people would've said being the central character in a huge movie franchise isn't in Iron Man's wheelhouse but that clearly changed.
And if we're talking about what's happening now is that Shuri is the current Black Panther so....
Last I remember Wakanda Forever was a great success but I guess I was mistaken about all the praise it received, and how well it did at the box office.