the trilogy it's in, and specifically Rise of Skywalker. For Last Jedi to really work, they needed to finish the story in a somewhat satisfying way. I don't blame Rian Johnson for ANY of that. Yes I would have loved for them to have has the trilogy planned out in advance, but that wasn't needed - the OT wasn't planned out like that. the MCU through Endgame also wasn't planned out film for film like that. But they needed to take the time to get Rise of Skywalker right.

Beyond how the trilogy went, my other issue with Last Jedi is with how Finn was handled. Part of this was because of the redirect in Force Awakens with Rey being the force sensitive future Jedi and not Finn as in the marketing. But there was still potentially a great story to be told with his character as an ex-Stormtrooper. They should have had him as the leader of a Stormtrooper rebellion with The Last Jedi kicking it off and Episode 9 making that a huge element of how they were able to defeat the First/Final Order. It wouldn't have even taken much of a change in Last Jedi check out this deleted scene, this is an alternate take of Phasma's death, with Finn convincing stormtroopers to turn on her:

https://www.youtube.com/watch?v=UzeIb-TZo_I

This would have been Finn's best scene in TLJ, and would have set up an even bigger subplot for Episode 9.