Lots of spoilers, cuz the plot of the movie is where I have problems.
Rey and Kylo Ren were fine. Luke suffered from character assassination, as far as I'm concerned. The action was fun, but no, it didn't influence the plot at all. In fact, Poe, Rose, and Finn's sideplot had literally no impact on anything. The introduction of Holdo as Leia's replacement, aside from being sudden, was made worse from the fact that she clearly had an axe to grind against the Heroes of the Rebellion. I like the idea that her perspective on Poe was that heroics can lead to needless sacrifice, but the way she demonstrated that was withholding information for literally no reason at all other than "ell oh ell, Poe is a dumb jock." He outright asks her if there is a destination, if they are headed somewhere or just running without direction. He is pleading with her to give him a reason to go on. Her response is "Leia would say have faith," with the "JERK" at the end of it unsaid, but, in my opinion, implied.
So Poe, Finn, and Rose go off on their own little subplot, making up a total of about, what, 45 minutes of screentime in a 140-minute movie? Not only is their mission an abject failure, but it was completely unnecessary. Poe's mutiny? Totally unavoidable. In fact, when Leia, you know, flies through space like Marry Poppins, and returns, all she does is tell Poe what the plan is. And his response is "Oh, cool. That can work. Let's do that."
In short, the entire internal strife among the Rebels is completely and utterly Holdo's fault. She holds back ABSOLUTELY NECESSARY INFORMATION for zero reason. As far as I can tell, nobody else knows this information either. And she knows desertion is a problem, since Rose apparently tazed a bunch of people before Finn.
When you have the meat of the plot of a movie be nothing but the result of "I'm not gonna tell you," you've got yourself a bad story.
Add on the fact that this whole movie seemed determined to undermine the acts of heroism we've had for seven movies. Luke's a hero of the Rebellion, but most of the characters (especially Rose, who couldn't seem to utter a single line without preaching in a terribly written attempt to make her seem deep, wise, and strong) would probably find his actions from the original trilogy stupid and risky.
In short, you can't undermine the value of the previous movies by implying the characters—beloved ones, mind you, characters that have endured four decades with their general reputations among fans totally untarnished—were stupid. Nor can the characters from the previous movie, which were bright spots—Poe and Finn, namely—have zero impact on the plot of the next one. If you removed them from this movie, literally nothing changes, except it's 45 minutes shorter. Hell, Finn's motivation doesn't even make sense. He wants to ditch the beacon to Rey somewhere, right? So he makes it off the ship to a planet that's decadent (where the film stops to tell you a Very Special Message about Animal Cruelty and War Profiteering is Bad Guys, Okay?) but relatively safe, and just... keeps the beacon with him. While he goes onboard the flagship of the First Order. He could've just tossed it into a trash can if that's what he wanted.
I loathed this movie. For me, it is a fresh black mark on a series struggling to regain its narrative feet after a disappointing prequel trilogy. Especially coming off the excellent Rogue One, I wanted my money back at the end.
Anyone is free to disagree with me; I'm not telling anyone that they're not allowed to like something, or that they're wrong for liking it. But the whole thing, start to finish, left a horrible taste in my mouth, and I just wound up mad. I get that they wanted to do something different, which is cool, but their way of doing that was mocking what was old. That's not fair; it's a slap in the face to fans of the original.