There were a few reasons why I felt it was not nearly as good as a lot of people are saying, and certainly not as good as Return of the Jedi much less the two masterpieces of the franchise, Star Wars and Empire.
The first is quite simple: the setup made no sense, and was ripped straight from the original. Why and how did the First Order arise after the events of Jedi? Why did the Republic allow it to happen mere years after the collapse of the Empire? Who are the Resistance and why would they have to be separated from the Republic? Why weren't they just the Republic's main army/fleet? If they were, why did they allow the creation of a planet which literally sucks in stars for energy and can destroy planets? On the part of the First Order, did no one give a thought to the fact that unlike a space station, a planet has no control system nor ambient heating for it's outer shell, and therefore A. the weapon could not move effectively, B. the exterior of the planet would be near zero degrees, and C. the planet could only reliably charge once before exhausting it's supply of local stars? Outside of the First Order, why would Luke leave a convoluted map to where he was planning on going? If he didn't want to be found why tell anyone, and if he only wanted those closest to him to know where he is, then why not just tell them? Where was Supreme Leader Snoke during the times of the Empire?
None of these relatively fundamental questions about the basic premise of the movie are ever answered.
The second reason I felt it was not as good as any of the originals was that the story was completely re-hashed from both the original and Jedi. Big weapon of the enemy, blow it up by any means necessary before it wipes out everything we hold dear. Only unlike in Star Wars or Jedi, the assault on the weapon felt way easier than it should've been, and far less interesting. As much as I hate the Ewoks at least the Empire had an entire legion of 'it's finest troops' defending it's shield generator in Jedi, not to mention an armada of warships to defend it from space attacks. The First Order had nothing. They let three inexperienced/old Resistance fighters plus a wookie into their primary stabilization center without any attempt at a fight (I think they shot like one stormtrooper on guard duty) and I don't think I ever again saw as many troops as I did when they raided some no-name village in the very first scene, even in the life-or-death defense of their greatest installation. In other words, everything about the final sequence felt like a cheap version of what we've already seen.
The third and probably most important reason is simply that the main characters' growth had no substance to it. Throughout the original trilogy, we see Luke cope with tragedy (the loss of his family), failure (his first stint of training with Yoda on Dagobah), and defeat (at the hands of Darth Vader in Cloud City). Through his experiences he grows and becomes a more complete warrior and character simultaneously. Rey just assumed her powers without any training whatsoever, and it didn't strike me as at all consistent with what we had previously been shown of the force. Now I'm sure that they will explain she is somehow like the next coming of Anakin Skywalker in terms of being incredibly powerful, but I feel like she should've had it at least as hard as Luke; no one would've believed if Luke had managed to trick the stormtroopers with a jedi mind trick when they escaped the death star late in the original movie, because his character arc hadn't gotten to that point yet. He still had much to learn and grow towards. I can't see how Rey has anywhere left to go that we should care about. Finn has similar problems, though at least his arc starts off with real growth and we see his struggle throughout the film with coming to terms with his past identity - and yet there's never a doubt that he has entirely abandoned his old ways. There's no real tension, just the threat that someone might be an asshole and hold his past against him, which of course no one does. And therefore all the tension in his identity vanishes as quickly as it was manufactured, and so in reality all he really did was get his ass kicked for two hours. I honestly felt really badly for him because he seems like the most relatable character in the entire movie, and yet he wasn't allowed any opportunity to grow as a warrior because he spent all his time getting saved by Poe, Rey, Han, Chewbacca, etc. I'm not sure how Finn is any different now from how he was five minutes into the movie, and I think that's an awful shame. Poe obviously doesn't undergo any sort of growth, and there's not any other new characters whose names I can even remember (outside of General Hux the caricature of evil and the old Empire, seriously I wouldn't be surprised if he's the son of one of the actors who played the exact same role in the original trilogy, except at least those characters had to cope with fear of Darth Vader and (in the deleted scenes of Jedi) actual moral dilemma with whether to blow up Endor in pure spite or not). The only character who grows is, well, Kylo Ren, who I will get to later on in this post once I start talking about the positives of this movie.
Luke had no speaking lines, Princess Leia was at best a spot character for nostalgia purposes only. R2D2 and C3PO were there for obligatory reference only.
In all, I guess that all of these complaints can be summed up as what I said earlier: the whole movie felt safe. They threw a lot of action in, constantly referred back to/plagiarized the original trilogy, and generally tried to deliver a movie that was as fun and thoughtless as possible.
