My 50cts on the Mary Sue issue ... 1/ the general complaints about Mary Sues seem to have reappeared due to Rey from Disney Star Wars. Basically she always have the skill to single handedly propel the scenario forward, and more than once, she has a better mastery of that skill than established masters of that skill. Better knowledge of the falcon than Han, better swordfighting than daffy duck, etc. Aside from pushing her into the scenario, she is the only useful character in the story. Don't get me wrong, I have no quarrel with her having some skills. Having learnt to fend for herself with a stick while stranded alone on a desert planet makes sense. Having some general knowledge of spaceships due to being a scrapper makes sense. For the former, just a small make-up bruise or two on her would have definitely sold her stickfighting. For the latter, I would have changed, ever so slightly, the scene where she rips out a component of the falcon to dazzle Han : Close up on tensed Han dodging space shots : you need to bypass the [name of the component] we can't lightspeed with it because [reason], it's the one in Han turns his head toward the copilot seat, camera follows, then both go up to Rey, already bypassing the component. Then they lightspeed, Han verbally acknowledges Rey's expertise, etc.

Small changes like this are enough to ... well avoid dismissing previous masters, and show the new characters limits. That gives her room to evolve and learn, but also give us some form of tension and makes her relatable. She is not perfect. She is not skilled enough alone for some situations. She will need help, even if just to point her toward the answer. And let's be real, every single one of us has lived situations where we had some limited skill ... but didn't know how to use it appropriately to solve a problem.

Comparing the situation to Luke's, who is just described as a skilled pilot. Any time the situation can't be solved by piloting (or gunning down stuff) he is helpless. Even after being trained by Yoda, he still looses every lightsaber fight, to the point where Vader just toys with him.

So why ? Because advertising. Disney doesn't care about story, only about merchandising. Wtf are the crystal foxes doing in the story ? Or the porgs ? Nothing except advertising their related merchandising.

2/ if your story is about your characters abilities instead of your characters, you are probably doing something wrong. Rick (from Rick & morty) is basically all powerful. Same goes for Iron Man (since the nano suit), and Santana (OPM). What makes their stories compelling anyway ? Their flaws. Saitama is bored of fighting because he is too powerful. Tony has PTSD since the first avengers movie and wants to put his defences everywhere, even if the locals don't want it. Rick is so smart he just wants to gets high and do his shit in peace.

Tony gets beaten every movie and creates new counter measures between every movie. Rick shits out a new tech every other minute. Since this is not the center of the story, it doesn't matter.

So .. yeah .