The Last Jedi is obsessed with the fallacious idea that in order to move forward you have to destroy everything that came before. It is as if someone walked into the Louvre and said "you guys need to stop holding onto the past," and then threw a torch down, cackling as hundreds of years of irreplaceable works of art burned to the ground, and then, standing triumphantly on the ashes, drew a smiley face.
In order to make room for the new characters to shine, Rian Johnson obliterates the character of Luke Skywalker to the point that Hamill himself couldn't recognize him; in the Original Trilogy Luke Skywalker transforms from a whiny farm boy into a hero who proclaims "I am a Jedi, like my father before me" and manages to do what both Yoda and Obi-Wan thought impossible: bring Darth Vader back to the light. In this film, Luke is tempted to murder his own nephew before he even did anything wrong simply because there is a chance he may turn to the dark side, but the worst thing is that after that rather than attempt to fix his mistake he falls into a pit of despair and hides on an island as his friends are slowly wiped out by the First Order. When Rey arrives he refuses to train her or help the resistance in any way (despite having made a map to his location in the previous film), until a strange out of character pyromaniac Yoda force ghost appears and tells him Rey is perfect already and also the extremely cliched line that "the greatest teacher, failure is." Luke is not the only wasted character from the Original Trilogy either: Chewbacca serves as nothing more than comic relief and Leia is incapacitated for most of the film after a strange Mary Poppins-esque stroll through outer space. Admiral Ackbar is killed so unceremoniously you barely even notice he dies.
The usage of the force in this film is wildly inconsistent with the previous films as well. First of all, force ghosts never were able to alter physical reality, yet in this film Yoda is able to bring lightning down from the sky, leading us to the question of why the force ghosts haven't just destroyed Snoke from their impenetrable positions in the netherworld. Leia is able to fly through outer space, and Snoke can force push people from across vast distances. Rey is able to lift multiple tons of boulders with apparent ease despite how difficult it was for Luke to make a single X-Wing in the Empire Strikes Back even budge. The force projection that Luke does at the end is actually interesting, but for some inexplicable reason they decide to make it kill him.
From a critical standpoint, the film is an incoherent mess. There is little to no character development and the plot is little more than a long, drawn out series of "gotcha" moments; we are treated like dogs, as Rian Johnson dangles delicious treats above us before rapidly yanking them away. In the climax of The Force Awakens Rey finds Luke and extends his lightsaber, but in The Last Jedi Luke merely throws the lightsaber over his shoulder. Leia is sucked into outer space, only to magically force fly back to safety. Luke agrees to train Rey, but then quits after only one pathetic training session. Finn is about to heroically save what's left of the resistance, but - surprise! - he is saved at the last minute by his awkward love interest. Snoke is the most powerful sith in any Star Wars movie ever, but is anticlimactically killed by a cheap trick. The entire first half of the movie leads us to believe Kylo Ren and Rey will join forces, but after Kylo Ren saves Rey - surprise! - they're not going to work together: Kylo Ren will remain the stereotypical bad guy and Rey the infallible heroine. Rian Johnson had a chance to actually do something original and daring in this respect, but instead chose to take the safe route.
The writing in this film is atrocious. Several lines are lifted verbatim from the Original Trilogy. The humor is out of place, overused, and sounds like they took the words of a heckler writing in the margins and thought they should actually put it in the movie (Star Wars meets Rocky Horror Picture Show). We are distracted by pointless subplots that are of no consequence. The new characters have no personality and sound like modern day buffoons who were simply transplanted into the Star Wars universe. There is so much wrong with it that you really just have to see it for yourself, although I would recommend not paying money for it.
In conclusion, The Last Jedi is the worst Star Wars movie ever made. It is heretical. It is the anti-Star Wars. It stinks.