She's a typical Mary Sue. Considering they're bringing back Luke and Palpatine, instead of sticking with Rian Johnson's vision, just shows they know they fucked up. That and they have no vision of their own. This will probably be fan service to the millionth degree. I'm skipping.
There were 99 other problems with the film imo, and I don't think anyone can confidently pinpoint any one particular reason for a course correction in IX.
I don't like how Rey got so strong before training, but that was honestly one of the smallest issues I had with the film.
And I'd wager the issue people feel more strongly about is how they handled Luke, given that his character has such a long legacy.
But in TLJ, Luke who would even see the good in Darth Vader,
considered butchering his nephew in his sleep as his FIRST choice.
Emphasis on 'first'.
That's just not his character. I didn't buy it.
And then there was the map to Skywalker. But
he didn't want to help out even when he heard that his best friend had been killed.
There were so many issues I had with that film, I'd have to write an essay to go through half of them.
And even if they revive
that doesn't necessarily mean J.J. Abrams disagrees with Rian Johnson's vission of Luke (although I would hope it does). It could also be because of something like Leia's actor dying, and they originally planned to have her play an important role at the end. But now they need a different character to fill that spot.
1) I think people misjudge Luke's personality quite a bit in Eps IV-VI and VIII. IV-VI Luke is incredibly naive. Even in VI. In The Return of the Jedi Anakin is still driven by the same thing that turned him to the Dark Side in the first place. To control chaos, to control the galaxy against those things he perceives as injustice, by force if necessary. Only with his son joining him would he be able to do what he wanted to accomplish, only with the imminent death of his son does he finally realize the folly, the futile nature of his goal, especially at that point.
That naivety carries Luke into his actions with his nephew. He has the vision of his nephews corruption and thus makes his hesitant decision, only to realize that that decision itself is what fulfilled the vision in the first place. A not uncommon theme.
I think is actions in VIII are fully within character. Nor do I see an issue with a map, pieced together from clues by people trying to find him on both sides.
2) Wracked with the guilt of his own failure he makes yet another naive decision that Jedi and their actions, his actions, will come to ruin. He shuts himself away in a remote place. VIII actually has a recurring theme that Luke incorrectly caries over from ep V. He will only make things worse if he interferes. In V he finds out about his father, he loses a hand, Han is trapped in carbonite, Leia is now slave to Jabba, etc. Finally at the last he decides to intervene and face the decision he made against his Nephew.
3) I highly doubt Luke gets revived in any sense. Force ghost sure, there is plenty of precedence for that. There is also plenty of potential lore to account for some influence of Palpatine to rear its head in IX.