Rise of Skywalker suffers from multiple issues, all of which make it difficult to watch unless you approach it from a completely "brain-turned-off" perspective. I'll try to avoid major spoilers in my review as I list them in great detail below. Buckle up.
1. *Very light spoiler* Emperor Palpatine's return. This not only makes no logical sense given his "oh lord thrown down massive hole into exploding Death Star" ending of Return of the Jedi, but as he brings a massive new fleet of Star Destroyers into play, it doesn't change the odds of the fight at all. The last movie left off with the rebels hopelessly outnumbered against overwhelming power. Now they are... In pretty much the same situation. Not only that, but Palpatine's... Relationship to certain characters feels cheap, derivative, and unearned.
2. The Stakes. Rise of Skywalker both ups the ante where it's not needed while simultaneously leaving the audience with little to care about. Think a new Death Star is not threatening enough? How about if every single Star Destroyer now has a Death Star cannon? That happens. A planet is destroyed... but with virtually no connection to it, we as watchers feel little. Not only that, but the one character on that planet who might have caused us to feel light sympathy at her death manages to survive.
This brings us to the other side of the stakes. Characters won't die. They constantly make "heroic sacrifices" while music swells in the background, but each time they are plucked back from death and so we are reminded that death has little meaning in this movie, with one or two rare exceptions.
3. The brutal reliance on nostalgia. Many places of old are visited, and many characters return for no reason other than to nudge the watcher and say "remember? Remember that cool thing?". The problem is, I do remember, and I specifically remember that those characters and moments felt real and imaginative when they first appeared on screen. The ending, without spoiling anything, was particularly egregious. It leaned so hard on the nostalgia of older movies that you could practically hear them creaking under its weight.
4. Toys. In this movie, we are introduced to vast variety of new Storm Troopers, Empire/First Order troops, and cute robots/ animals. *Minor spoiler* Hilariously, one particular group of new insidious villains stalks around the entire movie only for them to die like chumps in a 10-second montage. *Spoiler ends* the new characters, ships, and beings add virtually nothing new to the story, so why do they exist? Simply put, to sell merchandise. The movie pulls significant screen time away from where it could be put to good use with character-building, pacing, etc only because this way every 9-year-old might find themselves itching to get that new lovely "Jet Pack Stormtrooper" set.
Tl;Dr: Unnecessary new villains, bad stakes, reliance on nostalgia, and excessive marketing make this movie bad. Not the worst, but not good.