Rey actually has a pretty severe and destructive flaw in TFA; it just got lost in the shuffle and ignored by TLJ.
Rey is in severe denial about being abandoned on Jakku in TFA, and utterly refuses to abandon the planet and keeps seeking to return even though she objectively has no reason to return, and has it so bad she has a severe case of “refusing the call” in her Hero’s Journey and runs off in the woods and away from the saber, isolating herself away from aid... which begins the series of events that ends with her having been tortured and having her mind violated by Kylo, Finn having his back filleted open, and contributes to Han being killed.
Rey in TFA really is comparable to Captain Marvel from her movie, in the nature of her power level and hang ups; replace amnesia with abandonment issues, and ridiculously untapped raw power with ridiculously intuitive skill, and you’ve got roughly the same setup. But Rey’s also got the advantage of a more realistic mental flaw, a more equal (and in terms of what it actually took to take him down, more powerful) villain, and a script that is trying to portray her as more stunned and struggling with the developments than Carol Danvers. It also does bear mentioning that while she flies the Falcon too well and holds her own in most fights, she gets ragdolled twice by Kylo even before their duel - TFA *does* show him as a greater Force User and duelist than Rey, else it wouldn’t need him to suffer so many injuries, get so exhausted, and need to take it easy on end in order for her to win.
Now, that’s not exactly a flattering comparison in terms of her being overpowered or the story being perhaps obnoxious in its empowerment elements... but it’s not the same issues she has in TLJ, which go above and beyond that...
... And Ben Solo *does* become a Black Hole Sue when TLJ begins, upon whose the story begins to rotate and lavish praises and sympathy upon.
He killed Han because Abrams wanted to have a Villain’s Journey badguy who was an escalation on Vader... But Rian Johnson couldn’t bear to think of Adam Driver a loathsome villain, so he chose to just change the story around him. And that culminates in TROS, which resurrected Palatine to serve a Ben Solo’s redemption story, not because they wanted Rey to have a challenge, dumping a bunch of money in front of Harrison Ford so that Kylo can do over the killing of Han, and basically retcon the story in his personal history, and act as a new character.
Fanfiction OCs are just as often relatives of previously known character as anything else. That’s why Kylo being a Solo doesn’t really defend him from Gary Stu complaints... and does bring up one of my beliefs about the ST:
- Rey was almost certainly *originally* conceived, cast, and written as a Skywalker or Solo, where a lot of the things she does would automatically be chalked up to her heritage, as it was with Kylo, then Abrams thought she would need training from Luke concurrent to Kylo finishing his training with Snoke, ergo, Rey would get better at the Force in a conventional manner, have her story get more complicated in a conventional manner , and then probably lose the rematch handily to Kylo in a conventional manner (because again, Abrams and Kasdan through everything but the kitchen sink onto TFA to try and establish that Kylo was a greater threat than Rey but could be worn down, injured, and distract enough for her to beat him...
- And then TLJ came in, and screwed they plan up, leading to Rey simultaneously gaining even more power and skill with even less truckers and basically mocked the idea of training outright, while also simultaneously hallowing out her character to serve Kylo/Ben, who moves beyond simple Draco In Leather Pants when he takes the spotlight away from Rey at the end of the story to face off against Luke, because Rian Johnson really is apathetic towards her story and characterization, and thinks Kylo makes a better character, even though all he’s done is make the school shooter Neo Nazi would-be-Mind-rapist say “Luke started it!”.... and then argue that makes him sympathetic and more worthy of pity and attention than *literally everyone else.*
Basically... I’m arguing that if you think Rey is a Mary Sue, Kylo is also a Gary Stu... and probably the one that Rey was supposed to be originally, and is allowed to coast because the Skywalker and Solo name lets them hide his privilege and overpowered nature behind audience expectations.