Restructure the opening fight sequence to eliminate the explosives falling onto the dreadnought. There is no gravity in space.
If possible, Leia should die in the bridge explosion.
As other have mentioned, cut out Luke milking the thala-siren.
Reincorporate any deleted scenes of Luke and Rey interacting.
Replace Rey’s vision in the nether region of Ach-To. Incorporate an image of Snoke and audio of Palpatine uttering the name “Plagueis.” This could satisfy fans disappointed in Snoke’s missing backstory. Then transition to Kylo Ren’s attack on the new Jedi Order and Rey’s abandonment on Jakku.
Cut Yoda’s insinuation Luke never read the Jedi sacred texts because they were not page turners.
Either Poe’s mutiny should not occur or he should face at least some consequences for it.
As others have mentioned, streamline the Canto Bight sequence. After the hacker in the prison offers to help, cut to them flying off.
If possible, Finn should not attempt a suicide run against the enemy cannon; instead, he should retreat with Poe and the others.
Reduce the number of times characters say, “The last Jedi.” Preferably, the phrase should never be spoken.