I don’t agree it undoes ROTJ’s conclusions any more than the onward march of time “undoes” the actions (and the meaning behind the actions) of the people who fought (and died) for things in the past.
The endpoint of that line of thought suggests death makes life meaningless because once you die you lose, and once you lose, nothing you did matters. Which is kind of nihilistic at its core, and Star Wars has never been that. The story shouldn’t be ABOUT the story, it should be HOW it’s about it - if that makes sense. “Well, peace in our time only lasted 30 years so that 30 years was meaningless” is kind of a harsh, unfair, and cynical read that kind of minimizes the good that 30 years of peace can be.
I think the first two parts of this trilogy were kind of smart about how they were approaching a new conflict born of an old one, and investigating how and why new characters were handling those pressures, and what they were doing in response to them (and more importantly, why they were responding the way they were). There’s a lot that’s worth investigating in there, and a lot of that can (and should) speak to the times we’re living through now, for obvious reasons. That’s what myth does, it provides young people a means to make sense of the upheavals going on around them. That’s not so easily “nullified” by bad plotting, I don’t believe.
But The Rise of Skywalker is, unfortunately, thematically hollow, and THAT is a very big problem. It’s not really saying anything, and it’s not putting any effort into saying that nothing, either. It’s structural problems aside, the many problems with it as a movie - thematically it’s just a void, really. It’s good at saying what it doesn’t want to be, because it seems to have an idea of what people DON’T want, but it doesn’t have any sort of sense of what to provide as an alternative. So you’re left with a movie that is solely plot, for plot’s sake, wrapping up on a plot-level and nothing else.
THAT feels meaningless to me.
The idea that this movie could have been about a First Order fighting itself, and a Resistance taking advantage of that… there’s a larger thematic potential there that’s HUGE and relevant. You can easily build from “Knowledge and defense, never attack” and “Don’t fight what you hate, but save what you love” and elaborate from there in a story where the resistance finds a way to use the First Order’s nihilism against itself. That can MEAN something useful that ties into the thematic thrust of prior films, and Star Wars in general.
But instead the concerns were primarily “how do we fit deleted scenes in here and make a character out of that” and “How can we get the Emperor back in here so the parentage angle I don’t want to abandon takes center stage.” Those are plot concerns, not STORYTELLING ones, and the ultimate failing of The Rise of Skywalker is that its architects were more concerned about making their bad ideas fit into a plot no matter what than they were with trying to figure out how to actually SAY SOMETHING about… ANYTHING.