A lot of it has to do with her portrayal of Carol Danvers in the lukewarmly received Captain Marvel. The film’s overall plot was lambasted by critics as being “meh,” along with the writers choice in dialogue. Even before the movie came out, fans were rolling their eyes at the line, “I’m not going to fight your war. I’m going to end it.” This had comic book geeks asking how a war is going to end without fighting in it?
Carol Danvers does indeed fight in the film’s war (so she doesn’t find a workaround) and ends up being one of the Marvel universe’s most powerful characters, as she (he) is in the comics.
One of the most glaring problems Captain Marvel viewers had with the film, however, was Brie Larson’s “nonchalant” and “flat” performance of the character, according to some.
Fans clamored for a change in the character and tossed names several other actresses who they believe could’ve made the movie more enjoyable: Jennifer Lawrence, Emilia Clarke, Ella Balinska, Shailene Woodley, Kat Graham, Kristen Bell, Sophie Turner, Blake Lively, Laura Vandervoort, Julianne Hough, Zendaya, Katheryn Winnick, or Yvonne Strahovski of Dexter fame to portray Carol Danvers.
Source : https://www.distractify.com/p/why-do-people-hate-brie-larson