>could be that and maybe Marvel responding to plenty of fan
>backlash for Brie's generally weird shitty attitude toward
>some of the cast (and the awkward interviews she's involved
>with featuring other cast members, the Hemsworth and Cheadle
>one and the one with her and Renner are the ones making the
>rounds the last couple wks, also the insulting comments she
>made on Kimmel about hating some of the cast). could've been
>some damage control on their part, limiting her role in the
>film to just guest star status? maybe.

First of all, because the picture has absolutely been locked since those interviews came out. Second, both the Hemsworth and the Renner interview "shitty attitude" things have been waaaaaay overblown, largely by those upset by Larson's commitment to vocalizing about social issues. These white guy basement dwellers have been shitting on Larson since before Captain Marvel came out, looking for ways to try to shoot her down-- that's why there are a billion YouTube videos microanalyzing body language during a lengthy press junket tour aimed at proving something about how Larson sucks. Cheadle's already laughed off the work of these "Internet detectives."

She's not in it as much because, narratively, it makes way more sense to keep her on the sidelines in the final fight until she can get the applause-inducing grand entrance. These movies have often resorted to either sidelining the most powerful characters or finding inconsistent ways of knocking them down for lengths of time-- see also past treatments of Thor, Vision, Scarlet Witch, Hulk. Because if Captain Marvel, Thor, Hulk, and Scarlet Witch are all together at the start of the fight and make a cohesive plan to smash a gauntlet-less Thanos, and it succeeds as quickly as it probably should, then we don't get a big grand finale.

And, as you said, it's Iron Man and Captain America's movie, first and foremost. So they need to have the biggest moments earned.