Btw, worldbuilding? That's where I think both sequel moves have fallen short. I think if people were more engrossed in wider content, they'd stop trying to nitpick the number of skills people have.
It's not that it never gets used on men, it's just that people are far more likely to attribute problems they have with a competent woman character to 'Mary Sue'. Rey's no Thrawn, on a large number of levels, not dominating the narrative as much or having his overwhelming skill edge in his specialties. Rey's got two areas where she's, I'll call prodigy level (combat, force- though directly behind Kylo in both of those), solid to ok in some other levels (solid mechanic, ok shot), and not so good at some other stuff, plus wrapped up in some issues.As for 'Mary Sue' being gendered. I caught myself saying that Thrawn is a Mary Sue (or Marty Stu, in fact) the other day, at least in the reboot. This scene has particularly made me loathe the guy; where he beats up an armoured wetwork specialist who previously held his own against Wookies and Lesat in CQB, despite primarily being a naval officer who flies a desk. Fuck that shit, Thrawn shouldn't be that good at fist-fighting. I don't think I'm being mysogynistic hating Thrawn (who I fully dislike, unlike Rey).
Btw, I view Thrawn as a victim of his own hype. In-universe he's got a mythos as this unstoppable badass, but he picked a bad cause, overlooked things outside his area which came back and bite him, and did so little training of other commanders that it all fell apart when he died, even in mid-battle when they should logically be briefed on the battleplan if he actually had been showing them the ropes. Now he comes back and more of the memetic badassry has seeped in and now suddenly he's a badass fighter too.
Thrawn is, originally, not a Mary Sue, and nor is him being a 'Marty Sue' the problem even in rebels. No, the problem is he starts getting really good at stuff outside his narrative role. Is him being a badass combatant at all needed for him narratively? No. Indeed, it's something Rebels-him basically stole from his bodyguards- and in the original, "Having a whole species of uber combatants at your beck and call," is arguably more impressive and 'Mary Sue'-ish than just being a good fighter himself.... but, unlike his personal ability, it directly ties into his narrative purpose and background, so it works. One set of abilities is actually much bigger than the other, the other stands out more. A specific ability is the problem, not him being overall 'too good,' it's even a downgrade in major respects.
And here's another thing I've been trying to say- You leapt to 'mysogynistic.' Note that's not what I said- the fact that people respond to 'here's a gendered criticism, and I notice it gets deployed against woman more, and hey, people are latching onto it even when digging down there is a lot of factual problems with the argument,' doesn't mean you hate women, no, it means you picked up a brain-bug that exists because our collective cultural consciousness is full of dumb, gendered brainbugs that need to be picked out, and precisely 100% of everyone has some dumb ideas that they just haven't stopped to examine enough to toss out.
The fact that a lot of people have issue taking criticism on gendered issues is a problem. We need to be able to discuss gendered issues and lopsidedly-applied issues too, bringing up gender issues should not be specially exempted from talking about in cross-examination of stories.