What an obnoxious title for an article.
Mary Sue isn't the term I would use necessarily, but I think there's definitely a few problems with Rey. I mentioned my biggest problem with Rey earlier in the thread, but the thread is so long at this point that it's worth reiterating a few things-
My big issue is that Rey still hasn't had a real struggle, nor has she faced the consequences of failure. I find it really odd that some fans are almost gleeful about a mature, experienced Luke Skywalker still having huge flaws and a major dark side, but they have no problem with Rey showing no signs of even having a dark side through two movies. . On the one hand people talk about how she's the hero, it's no longer the OT trio's story, etc., and yet she's the only one who has everything figured out and isn't actually having a character arc.
People talk about her "failure" with Kylo. Well, she got at least as close to success as Han, Leia, or Luke managed, and frankly Kylo has been pretty much unconvertable up to this point in the saga. He feels the pull of the light side, but he makes a conscious choice to be dark. She can't help that, and given what we know about the light and dark side her choice isn't even that fool-hardy.
What was the consequence of her failure? The death of the most powerful villain in the ST. Contrast that with the darkness that Luke faces in The Empire Strikes Back- Rey never comes close to the same depth. At this point, I wouldn't even discount the idea that Rey isn't an actual person, but is a manifestation of the light side without darkness or fear.
As for training- no, Luke didn't have much training, but I have a problem with Rey being able to pull off sophisticated Force maneuvers with no training whatsoever. At least Obi Wan told Luke how to use a lightsaber and Yoda taught him some Force basics. Through two movies, what useful advice has Rey actually been given (and used)? Luke's bad advice is worse than no advice at all.
Daisy Ridley is very likable and so is Rey, but I wouldn't hold it against anyone who feels like Rey's perfectness and awesomeness is being shoved down everyone's throats to the ultimate detriment of the character.