Those kids weren’t killed in the movie. They are still out there. It is heavily hinted at that Finn is force sensitive so new people not connected to Skywalker/Palpatine will still be able to use the force in the future. They just weren’t the focus of this movie and shouldn’t have been.
The force basically works like magic in Harry Potter. There will be muggles who learn to use magic. But there are also powerful bloodlines like Dumbledors, Potters, Slytherines.
It’s a star wars movie. Redemption is a key theme. Like Return of the Jedi being about Vader’s redemption, Kylo was always going to be redeemed in some way.
The emperors return happened off screen. Not necessarily a retcon. A lot happens off screen or in the years between Ep 6 & 7 and 8 & 9. I am sure we will now get a whole bunch of new books and comic books filling in the gaps. But the seeds for his return were laid all the way back in Ep 2 when it was Palpatine that mastered the creation of a clone army and Ep 3 where he hinted that he knew ways to conquer death as a Sith.
We aren’t given an exact timeline to Luke’s exile. His search for the Sith homeworld could have even been before he started a Jedi school. There’s 20 years between Ep 6 & 7 he could have gone searching for it. And since he didn’t find it it’s hardly worth mentioning in the past 2 movies.
Yes they should have done something more with Rose. She could have at least been on the Falcon.
He broke the mask in a fit of rage by being embarrassed by Snoke. With Snoke gone he can resume wearing it with confidence. It might even help him hide his conflicted feelings about being SL and Rey as Snoke implied.
Rey had the broken lightsaber by the end of Last Jedi. It’s so impossible to believe that Rey could rebuild it while being trained by Leia who its revealed built her own lightsaber or from the Jedi texts?
Where did Luke get his lightsaber from between Ep 5 & 6? Nobody questions that.
I agree that Rise of Skywalker is pretty flawed. And it does rely on a lot on telling and referencing things off screen rather than showing. But I guess I don’t agree with the narrative that it’s somehow an erasure of Last Jedi.
Plus the Star Wars cannon is full of revisions and holes. Its not a nice, perfectly laid out 9 episode story. But it was already full of gaps before episode 9 and it seems like people are holding it to a higher standard than other parts of Star Wars that don’t make sense.