I loved The Force Awakens when it came out. I still love it, even now when so many have turned against it. I think it's a fine addition to the collection. But The Last Jedi just pisses me off. Rian Johnson doesn't understand character in the slightest. He just engineers things he wants the characters to do, and then railroads the characters down that path kicking and screaming.
Rey. Re-watch TFA and you'll notice something. Not once does Rey say she doesn't know who her parents are. We, the audience, don't know who her parents are, but Rey never gives any indication she doesn't. She can clearly remember them leaving her when she was a child, and she's waiting for them to come back. Her character arc in TFA is about letting go of the past and moving forward.
But come TLJ, all she can do is dwell on the past, on her mysterious parents who she suddenly doesn't know. Until partway through the film when Kylo tells them they're dead nobodies, and then Rey repeats her arc from TFA. She should have already been at that point at the beginning of the film, but it takes until the end, after she's already left Luke, for her to finally accept that she needs to move on. Her arc is wasted.
Finn. In TFA, he's a stormtrooper, abducted and brainwashed as a child to fight for a cause he doesn't believe in. His first experience with battle is so traumatic he flees the First Order at great risk to himself, and then when he meets Rey, he lies to her about who he is, because he's scared she'll either judge him or not help him. When they get to Takodana, he jumps ship at the first opportunity, signing up with a ship that's about to leave. He'a a selfish coward. His arc completes itself when he chooses to come back to help Rey, and then later chooses to infiltrate Starkiller Base to save her and help the Resistance.
But come TLJ, just like Rey, he's reverted back to how he was at the beginning of TFA. He's a coward, he's out for his own head, and he has little desire to help the Resistance in their fight. In fact, he has to be lectured on how child slavery is bad by Rose. The ex-Child Soldier has to be told Child Slaves are bad by the girl who's never seen a battle in her life. Yadda yadda yadda, pointless animal racing and Phasma slaying side quests, and by the end of the film Finn is once again ready to put himself in harms way to help the Resistance.
Kylo. His arc in TFA is much simpler. He's bad, but not all bad, he's conflicted, maybe he turn back to the light side. But then he kills his father, and "completes" his training. He's Team Evil now, ready to destroy the universe and be a compelling villain.
In TLJ, he, too, reverts back to the troubled, conflicted state he was at the beginning of TFA. He hesitates and ultimately fails to fire on his mother's ship. Rey still thinks there's good in him, and she goes to meet him. She tries to pull him back to the light, but then he murders Snoke and once again goes full Team Irredeemable Evil, ready to destroy the universe.
It's absolutely infuriating to see that Rian was so creatively bankrupt that he couldn't develop the characters past where they were at the end of TFA, instead reverting every last one of them back to their original status quo only to tell the same story with them a second time.