Sure, it's not the best movie ever made, but not terrible enough for some people to start an online petition to strike it off the official canon...
It's not so much that it's a bad movie that would warrant striking it from the canon, it's all the things that it introduces to the Star Wars universe.
It destroys the character of Luke Skywalker by giving him this un-Luke Skywalker-ish history, and then kills him off for no particularly good reason. If Luke-freaking-Skywalker can randomly be drawn into trying to murder his nephew, I'm not sure there's any point anyone bothering to try and resist the Dark Side.
It introduces the ultimate weapon of light speed objects, which largely invalidate all space battles up to this point since the invention of hyperspace drives.
It introduces a hyperspace tracker, which even if it's only just come into existence is a nightmare of a thing for a future writer to deal with. Now anyone trying to get away from the First Order has to have a reason why they can't be tracked through hyperspace.
It establishes that one can be a master of the Force with no training or experience, and can defeat powerful opposition that has been in training for decades. 🤬 Rey and her magic powers. At least Anakin and Luke had to work for it.
It establishes that Force ghosts can lightning strike the real universe. Roll on the unstoppable army of Force ghosts.
It does away with any attempt to tie Snoke and Rey (two of the most influential characters of the era) into the universe. Snoke is a guy who died. Rey is nobody. This is strongly at odds with how lineage and history have been treated in the past films. Who you are and who trained you was very important in Episodes 1 through 6 and the Extended Universe. Kylo is the only major character with a back story.
It establishes that both the First Order and Resistance are led by morons. Not just at the top either, several levels deep at least.
It reduces the Resistance to one ship of people with no allies remaining. Seriously, the Resistance is done. Rey might be magic, but she can't take on an entire evil empire by herself. The movie is the bad guys winning, and any come back from here is going to be implausible.
There are any number of problems with the actual plot of the movie, but the things that it introduces to the universe make it a freaking nightmare for anyone else going in afterwards. How hard is it to create a decent movie for Episode 9 given all that took place in TLJ?
Damn near impossible, I'd say. You've got a ridiculous underdog Resistance who are somehow going to have to win against a galactic empire, you've got magic Rey, you've got that any military problem can be solved with hyperspace missiles, and you've got that anyone can be tracked anywhere. It's really hard to create any sort of plausible tension with those in place.
I'm not sure the best writer in the world could do a good job with the Star Wars universe in current state, which may be why there's such a push towards films and media of earlier history where they don't have to deal with the ridiculous shenanigans introduced in the sequels.
D
