Steering clear of spoilers is almost impossible, but I will do my best to review this movie in abstract terms:
Rise of Skywalker is two movies crammed into one. It's fast-paced, yet feels slow. After the fan backlash on Episode 8: Return of the Jedi, Disney tried to undo some of the developments from that movie. Hence, the first half of Rise of Skywalker is course correction. I myself did not like Return of the Jedi at all, but it at least had a handful of spectacular nerd-gasmic scenes. Rise of Skywalker, unfortunately, doesn't even have that silver lining.
My biggest problem with this movie, and all the other sequels (e.g., the new Terminator movie), is that they tarnish childhood nostalgia and good memories that we had by rewriting the past. In the particular case of Episode 9: Rise of Skywalker, we see (spoiled in the trailers) the return of Emperor Palpatine. The fact that Palpatine is still alive, means that Anakin Skywalker (the redeemed Darth Vader) was NOT the promised Chosen One... His sacrifice did NOT bring balance to the force - the balance did not even last for a full generation... He did NOT end the Sith... Hence, there is no end to the struggle between Jedi and Sith. It is an inevitable fate that is going to repeat itself over and over and over again. There is no finality to the story, which negates the significance of any victory or conclusion.
Jenny Nicholson, a Youtube personality, has listed all the flaws of Episode 9 masterfully. Therefore, instead of repeating a subset of those points, I'll just embed her analysis below:
I understand why Hollywood doesn't take risk in new intellectual properties (IP) and wants to invest in what is proven to sell. I wish they rebooted the Star Wars or Terminator IP - like how we have a new Batman every decade, and it does not affect what the previous ones meant. Or if they made these movie franchises procedural like James Bond movies where every movie is just a new standalone mission.
All said, Rise of Skywalker has to be seen by everyone who has followed the franchise. It is just an Okay movie worthy of a 6/10.