Jesus christ, it's going to be two and a half fucking hours of lens flares, member berries, and disjointed aping of the OT's conclusion, but with none of the emotional payoff of having seen Luke complete his journey. Rey has not changed at all and due to her nature as a perfect Mary Sue Snowflake, cannot improve in any way, shape, or form. There's nothing to celebrate when she inevitably defeats Kylo and the Emperor and the entire Dark Side of the Force in a stunning display... because we were here from the start. Nobody cheers at the start of a marathon, and yet, Rey is still sitting right where she started.
If Rey wins over Kylo Ren in this movie, there is literally nothing to cheer about. She bested him several times by now, so there is no tension here.
There is also no personal struggle of any kind since there's nothing distinct that she's trying to achieve. "Defeating the bad guys" is too vague and not her personal motivation.
She gave up on finding her parents in TFA. She gave up on finding them again in TLJ. Now, IX will give us some "She was a Skywalker all along!" plot or she'll give us a "She's a granddaughter of Palpatine all along!" plot. We've fucking abondoned the "Rey's parentage" plot twice already, why bring it up a third time, it should, by all accounts,
mean nothing to her.
What else is there to really define her character, to give her a personal goal to work towards?
When Rey finally wins against the First Order and redeems (or kills) Kylo, it will not really feel like much, since there ar no stakes. No personal investment. It will feel like she's going through the motions of the plot.
And of course, there's barely any place remaining for her personal growth as a character since she lacks a character and personality. You said that in the "Marathon" of the plot she's were she started and thus there's no reason to cheer. The problem is: She already started behind the finishing line. We don't have to watch her overcome herself and become capable in using the Force, she already has achieved that non-chalantly with great ease. She's already at the goal, on her way to the podium, while the race officially isn't even over yet. And when you point out that it's bullshit that one of the runners started right behind the finishing line, you're branded a bigot. Here's something funny:
Imagine an alternate cut where Rey is a long-lost Jedi Master, what changes would it take in the movies to accomodate that?
She's already using whatever Force ability she needs at the moment she needs it perfectly. Changing Rey, someone who supposedly doesn't know what the Jedi even are to a Jedi-master, should shift her character to an absolutely ridiculous degree and alter the story completely, but when you really think about it, movie-wise nothing much changes. A few lines of dialogues at best. All her actions remain the same. At no point would you go "Here, she could really profit from doing Jedi-Stuff" cause whenever she's in need of a Force ability, she just pulls it right out of her ass.
Being tortured and questioned by Kylo? She just defends against and even turns around the mind reading.
Captured and held prisoner? She just uses the mind trick.
Has to fight back an angsty Sith-Lord-fanboy-school-shooter with a light sabre? She easily fights him off.
You could even say that her amazing flying skills are part of her Jedi-Powers...
And even though Disney was running the mills of paid Journalism to fight back against the well-earned label of Mary Sue, they are aware that this is a huge criticism against Rey...
So, what I expect: Rey will have a downgrade in power or a few failures in the first and second act of the new movie. Then, she'll overcome the spontaneously errected limits and the movie will treat that achievement, even though she's done things of a similar calibre multiple times already, but Disney has no choice, they need to pretend that she's not perfect and all-powerful, they need to cram some pretend-character-development into this thing.