To me it's pretty simple, Brie Larson just isn't an athlete.
Movie magic can do a lot. Damon looked like a ninja in the Bourne series and plenty of other actors have been able to portray athletes, but sometimes it's clear that they just aren't. Chris Evans, Hemsworth, Jeremy Renner... those guys are legit athletes. So it looks natural when they are doing superhero stuff. Brie Larson doesn't really pull it off, when she runs it just looks funny. It's not a huge deal, but for some its noticeable.
And so Brie doesn't think I'm being a sexist, the other women of the MCU pull it off and really well. Zoe Saldana and Evangeline Lilly are straight up studs. They look legit when they fight and run. I actually think Scarlett Johannson does as well. Gal Gadot is definitely an athlete too, so even though she wasn't built like Wonder Woman and a little skinnier than what most people wanted, she could do the stunts and choreography really well.