It's a fucking story guys of course it's been deemed worthless. Lord of the Rings has a satisfying conclusion. Star Wars had a satisfying conclusion - not anymore.
Hey guys did you know 30 years after Gandalf tried to murder a boy. Did you know that Sauron AND Saruman came back, except this time there towers where 1000 times as big. Did you know that Aragorn did fuck all as ruler. Did you know that Sauron had another ring? Now some new hobbits must go an adventure and destroyed it once and for all!
Pretty much.
I'm tired of the lazy argument that, "nothing lasts forever and pay attention to history." First, Star Wars isn't real life. If Rey, Finn, and Poe were all vaporized by a random passing photon torpedo on the battlefield I doubt you'd just shrug and go, "welp, that shit happens in real life. Good guys and heroes don't always win or survive in war." So, that argument is without merit.
The second lazy argument is that the series is called STAR WARS thus conflict and war is inevitable. Again, this is a poor argument that creates a strawman for an easy rebuttal. No one is saying that SW films should be without conflict, they're saying that a new conflict so soon after our OT heroes last victory, a conflict that completely negates their victory, is poor taste.
There could have still been a new conflict without completely destroying the New Republic, creating the Empire 2.0, and completely destroying the Jedi Order, again. This isn't just some new conflict, it's the exact same conflict our heroes won. It tells us that they all utterly failed. And, they couldn't even get a decade of peace. Remember, the war didn't end with ROTJ. Five years after that they were still pushing the Empire back. Then when they finally won and the New Republic came about, they got a few years of peace before TFO showed up. So, the "peace" was beyond fleeting.
It's understandable that people are upset that there heroes failed so completely so soon after their victory. As another pointed out, it's like Sauron's brother coming back and fucking up Middle Earth a few years after ROTK. It's nonsense.