Can be anything, from characters not using objects they have on them, to physics not being realistic, or a very big plot hole.
As an example, one of my friends told me that his pet peeve is that in a lot of sci-fi movies, when spaceships run out of fuel, they stop moving, while inertia and lack of atmosphere should keep them in motion.
Oh nooo he crushed one of seven thousand mystery boxes, all of which had disappointing contents anyway.
JJ’s not even smart enough know Palpatine would be scarier staying dead. An immortal Force ghost whispering to people anywhere in the galaxy is a proper villain. A zombie who did all the bad stuff by himself is a cartoon. Especially if all the bad stuff unhappens if you poke him with a laser-sword. And people have the nerve to wish that was two movies! The silliest defense of 9 is that it would’ve been better if it was longer.
If 8 had been “Star Wars with the serial numbers filed off,” like Rebel Moon, it would have fucking incredible. A royal-led uprising that beat space fascists and then utterly failed to stop them forming again is now on its last legs, and even the decisive battle is a low-speed chase toward inevitable failure. The protagonist, an idealistic young soldier, loses someone close and stops a deserter “or they died for nothing.” Those two risk some hail-Mary espionage that shows war profiteers win either way. Disillusioned in the cause, she gets an unsubtle scene freeing their animals. That plot ends with her ditching precious materiel to stop him from repeating her sister’s sacrifice, and should end with both of them deserting together. But “whoops nevermind.”
Meanwhile: the assumed hero finds an old space-wizard veteran for training, and he bluntly tells her to quit. Wars (do) not make one great. So she goes straight to the dysfunctional bad guys, whose hate-based leadership structure turns out to have issues, and the suddenly-in-charge guy tells her that her mysterious ancestry doesn’t fucking matter. Nobody hands you a destiny. You make your own choices. As illustration of this, he offers to make her empress of the galaxy, and also as illustration of this, she tells him to go fuck himself.
Meanwhile: the good guys’ hope-based leadership system also has issues, and ‘just trust me bro’ nearly gets them killed faster than how they’re obviously about to get killed anyway. They find a corner to back themselves into by deleting the bad guys’ flagship with the coolest moment in all of Star Wars that completely does not work within the logic of Star Wars.
And what should have happened is, the hero arrives to find the battle over. The bad guys have been through and there is no sign of survivors. But what happened is, some nameless rando saw the crystal foxes casually weave through boulders, and learned to use the Force in a fucking hurry. Because again: it is is in all living things. That’s the message the wizened veteran literally smacked into the hero, passed onto him by a sassy frog on planet ketamine.
What happens instead is that of course the hero shows up and does it for them. Fuck themes, right? Not like the movie opens and closes with untrained Force use. Including that shot of a slave child looking to the stars. Subtle as a brick through a window, but god damn, does it work. Shame it’s in the movie we got.