There seemed to be a portion of fans complaining the Last Jedi had been 'panderings to SJWs' and had too many prominent female characters. Around the release of Captain Marvel, I think Brie Larson was meant to have said something complaining about the all male crew on the movie or something like that.
So her being in Star Wars is likely to pour more fuel on the alt-right fire.
In reality it's more likely its that Feige gave her a call having worked with her on Captain Marvel. Directors do this all the time (Chris Nolan being a great example).
Lol, alt-right? It's hilarious how they have become the Boogeyman you can blame all of your problems on, now. Or just label anyone you disapprove of. Dislike of TLJ cuts through the complete political spectrum. It also had nothing to do with prominent female roles, but how they treated the male counterparts. Of course, the biggest sin was it's shitty plot and how it ruined Luke's legacy, as well as any good mysteries that TFA set up.
As for Brie Larson, she decided to insult all white men, saying their opinions didn't matter. Especially when it came to films that "weren't meant for them," like A Wrinkle In Time. Of course, it was just a shit adaptation of a novel written by a white woman who definitely would have spoken out against that message if she were still alive.