I think part of the "hate" towards Brie Larson is due to a comment she made at a press conference a few years ago where she expressed an interest in seeing a more diverse group of journalists asking her questions. What sounded reasonable was taken to be an insult by many online, and hence the hate.
An example illustrating her point is this review:
The Marvels Reviews Film Threat - Part 2
NOW IN THEATERS! Ironically, The Marvels is about as fun as a cat and a laser pointer (which appears in the movie). You'll chase the story only for so long before you realize there's nothing there. Our tale opens with the Kree leader Dar-Benn (Zawe Ashton) searching for a powerful wrist...filmthreat.com
where the conclusion is the following (as if teen girls can not be comic book fans):
"In the end, The Marvel is a superhero movie clearly made and produced by people who have never read a Marvel comic book but read Archie instead. It feels like it was made for teen girls and not for actual comic book fans."
Whatever merits the review had, I think, is lost in that conclusion.
Not that I think anyone should use such a stereotype... but it probably gets the point across succinctly and reasonably accurately though (regardless of whether one agrees w/ him/her or not about the movie).
The movie clearly plays like it's targeted more for that demographic than any other IMHO... and I'd say the poor box office performance probably reflects that to a great extent -- that's not to say nobody other than teen girls will like it of course (or that most teen girls will like it either)...
_Man_