This trilogy firstly shows no firm foundation for its main characters, Rey, Finn, and Kylo Ren. Rey is just a scavenger girl who "turns out" to be very talented in the Force and even in Lightsaber skills without anyone teaching her anything. The only real "teaching" she received was the bullcrap comical conversations she had with Luke Skywalker.
By the way, how on earth did Luke Skywalker turn into a Darth Vader-saving "New Hope" of the series into a man with crippling depression who nearly killed his own nephew for having a few evil dreams?
Finn is just someone who turned against the First Order, and may have the best reasons to fight them out of all the characters in the movie, but I still don't understand why the hell him and Rose went all around the galaxy, barging down space casinos? It had literally nothing to do with the main plot.
Kylo Ren is the worst one. He is just a masked, emo man with the mindset of a teenager; kills off his own father(Han Solo; one of any Star Wars fans' favorite character) like nothing, always gets shredded by a scavenger girl with no real training, attempts kills off every single O.T character because the plot wills it for absolutely no good reason, and is just a disgrace to his grandfather and his family's name. As a character. It would have been better if they just brought Darth Vader back to life with no real backstory to it. That's how bad Kylo Ren's character is throughout the series.
All in all, The Last Jedi is not even worth a single star.