I think Kylo Ren's nature as the villain of the piece helps feed into this.
I tweeted something a couple days ago that took off pretty decently:
and I think that gets at the core of why some people are out of hand rejecting her competency and victories in the film.
Kylo Ren isn't the traditional "badass" bad guy. If anything, he's more like a metatextual commentary on shitty Star Wars fans, who take all the wrong lessons from the story being told. There are a lot of people who, whether they consciously realize it or not, see themselves in that misguided, stubborn, mean-spirited, scared character. It's why his appearance shocks the shit out of people. He takes off the mask and he looks like... a cosplayer way too into his persona. Which is what he is. He's not a badass. He's not the power-fantasy he wants to be. He's closer to a fuckin School Shooter than anything, a stupid, shithead kid who thinks the only way he can be special is to ruin everything good for whatever silly reasons he's decided to latch onto.
So
that's unpleasant to a lot of people. Then combine the fact this girl, who is essentially the personification of the Luke role in the first film, but maximized and made more dynamic in a couple ways, defeats him outright. Not just mentally, but physically as well. Granted, he's handicapped during that fight, but she wins it clean, with the help of The Force.
What you're seeing are people reacting to not just the defeat of a Male Power Fantasy, but the defeat of a very specific Male Power Fantasy that is kinda laid bare as the wimpy, shitty falsehood it often is, at the hands of a character who normally (and to their mind, by all rights probably SHOULD be) is a guy, but isn't.
For a lot of people, I think what they're really reacting to is the fact their normal
in to this fantasy world is now shut off. Of course, it really isn't, they just can't concieve of allowing the woman (or the black guy) to be their surrogate. So the criticism then gets poured into how stupid it was to make the villain an accurate, creepy representation of all the wrong things about that power fantasy, and how stupid it was to allow the girl to inhabit some of the same traits their favorite heroes consistently inhabit.