I liked it, and to some degree was trying to really make out why, and then
I read this. I think it really kinda sums up what was different.
This film [mostly] wiped the slate clean. "The Force Awakens" was about tying these new characters into the past. "The Last Jedi" was about those characters starting their own, new, future. In Awakens we saw the end of Han Solo. In Jedi we saw the end of Luke. And despite not getting any fan service about Snoke's background, we knew he had *some* background but now Kylo Ren is essentially free of his past, be it Snoke, Han, or even Leia. And Rey's parents being nobodies gives her a fresh start.
Back in Phantom Menace, Anakin basically came out of nowhere from nothing. Granted because of the original trilogy, everyone knew who he was and what he was to become. But he was off-the-charts force sensitive, the one who could "bring balance to the force". Rey came out of nowhere from nothing, and although her power seems to be absurdly strong [as a teenager], that's not necessarily different than Anakin who was racing the pod racers and flying spaceships at the age of ~10 in Phantom Menace.
I think what I like about this movie is that the characters in the prequels already had their stories written. We knew what Anakin would become. We knew that Obi-Wan and Yoda were the last vestiges of the Jedi after some calamity. But we don't know how this story is going to develop. We know Luke is "gone" [although he'll undoubtedly make a force ghost appearance]. We know Leia will have to be gone. We know now that despite Kylo Ren's lineage, he has freed himself from the anchors of the past and is becoming his OWN villian. Rey has to face him without Luke, and must essentially supplant the little training she had from Luke with the Jedi texts. And they teased the bit at the very end where the little boy force-pulls the broom to his hand to suggest that maybe the next movie won't ONLY be about Kylo vs Rey.
The Force Awakens was fun, but it wasn't all that exciting. Because it was predictable, even to the point where as soon as Han faced Kylo Ren you *knew* he was going to be killed. The baddie [Ren] was just a puppet of a shadowy master. And shocker, the movie came down to plucky rebels destroying the Death Star -- the only change was that the Death Star was an entire planet.
The Last Jedi broke all that. And it needed to. Because since the original trilogy 40 years ago, the story has been a little too stagnant. Even The Force Awakens was about Luke, Han, Leia and Vader. Now the story is about Kylo, Rey, Fin, Poe, etc. It's once again new.