Well you have current box office.
Captain Marvel marketing was specifically tied to the Avengers Saga.
It's a different film, with different leads, released in a different time (post-COVID, post high point of the MCU), and .... wait for it ... DURING THE SAG-AFTRA STRIKE so that none of the stars could do promotional work for it.
The basic problem (which people have been hinting about, some overtly, some less so) is this-
There are people who are making the following argument....
If a movie has a white male lead, then it's just a movie that can be judged on its merits. It can succeed, or flop, because of "regular reasons," ... you know, script, directing, VFX, timing, zeitgeist ... all the factors that make or break a film.
On the other hand, if a film has a woman or minority as the lead, then it's always a referendum on that person's ability to carry the film. And every success is for reasons external to the person, and every failure shows that they can't carry the film.
Which ... is why there is a bit of pushback going on. Captain Marvel and Black Panther were the two most successful MCU Disney movies that weren't Avengers movies, and yet we hear the constant refrain that every single movie is a referendum. Daisy Ridley helped relaunch the Star Wars universe, but when she was let down by corporate idiocy and infighting (and still had billion+ grosses for the next two films), she can't carry the movies. And so on.
People have been gently trying to point out the weird and unfair standard. Margot Robbie was always a great actress- yes, even before Barbie. The success of a movie depends on a lot more than the lead, and ascribing the failure of movies to gender and race of the lead is something we really should have a gimlet eye for.