The Last Jedi had some very specific issues and it wasn't the Luke movie I've been waiting for, but the overarching problem is a lack of mythology. If the movies and the 'Legacy' books taught us anything about this universe, it is everything is connected. You know the whole theme of the 'force'. I never really thought about the series being centered on the Skywalkers, but more of this web of events that are all part of one large story. This last movie really broke that for me. Rey should have been a Kenobi, Palpatine, or a distant cousin to Darth Maul. Something to tether her to this universe.
The cynic in me believes that this was absolutely originally planned, but either the online community correctly guessed it early on or came up with so many better origin stories that the writers scrapped it. The same could be said for Supreme Leader Snoke. JJ Abrams set up all these great stories to be flushed out and it felt like the next guy didn't want to deal fan backlash for a disappointing ending. So he just said "Lets skip that and just make it fun." And it absolutely is, but for those that have been following this story for a long time, this felt like a cop out. There is still another chance though. Help us JJ you're our only hope...but please don't just remake Return of the Jedi.