Moving on from the Skywalkers
The first six episodes of the Star Wars franchise focused solely on the Skywalker saga. Sure, the previous films had heroes with different lineages, like Han Solo, Obi-Wan Kenobi, and Lando Calrissian. But nevertheless, the Skywalker clan drove the action. The Force Awakens was the first episodic step away from this, choosing to focus on a group of newcomers (and Han Solo) instead. But even that film kept strong ties to the galaxy's first family, with Kylo Ren being revealed as a Solo/Skywalker and Rey's parentage being left open for a potentially major reveal. The Last Jedi, however, takes truly meaningful steps to expand the universe beyond the bloodlines of Anakin Skywalker.
Obviously, TLJ's biggest move in this department comes with the death of Luke Skywalker. The farm boy who came from nothing and went on to save the galaxy from tyranny is dead and gone. What's the galaxy to do in the face of the First Order? Turn to a handful of new heroes that came from nothing, that's what. The reveal that Rey doesn't hail from a special lineage made for a far more compelling twist than 'she's Kylo's twin!' or 'she's Obi-Wan Kenobi's granddaughter!' ever could have. Fellow new trilogy additions Poe and Finn aren't anything special either, further proving that true heroes can come from anywhere. Your father doesn't need to have had a super high midi-chlorian count in order for you to matter.
In fairness, two Skywalker ties do remain by the time the credits roll on TLJ: Leia and Kylo Ren. The former's return is highly unlikely, of course, given Carrie Fisher's death. (Hopefully, Leia will be given the graceful end she deserves.) Kylo will likely stand as the only character in Episode 9 with Skywalker blood. He's being set up as the conflicted main villain, a la Darth Vader, but since that's the one person he truly emulates, at least that makes sense. But if he bites the big one in Episode 9, the Skywalkers will be gone forever.
A world that's not so black and white
The never-ending battle between good and evil is a crowdpleaser, but we've seen it more than enough at this point. All seven of the previous Star Wars films drew clear lines between the good guys and the bad guys. The Last Jedi definitely has its share of heroes and villains, but it has the guts to both do away with the one-note baddies (Captain Phasma and Snoke) and add dimensions to its heroes (Luke) -- even if those added layers don't make them all that heroic.
The heroes of TLJ frequently end up making the wrong call. Luke never should have pulled an Obi-Wan and abandoned the galaxy. Finn, Rose, and Poe's plot to take out the First Order's warp-tracking abilities was woefully undercooked. Rey delivering herself to the First Order in an effort to turn Kylo could have backfired spectacularly. Our heroes consistently set themselves on doomed to fail courses, but that's what ultimately makes them more relatable than previous heroes in the Star Wars universe. They're almost unreliable narrators in a sense, but they're more compelling.
Aside from killing Luke, TLJ's gutsiest move was removing Supreme Leader Snoke from the equation. Two years of fan theories were flushed down the drain in a single Force push from Kylo Ren, killing off Snoke a full movie sooner than you think. Why? Because he wasn't half as complex as Kylo. The former Ben Solo has an actual arc, and his unpredictable behavior makes the final act just as unpredictable. It will do the same for Episode 9.
This may not be the feel good 'good guys win, bad guys lose, roll credits' universe you've grown accustomed to. It's far more complex than that.