Because Luke really isn’t in the film, TFA really seems more like a prologue to the real story than part of the story. It really just introduces us to the new characters and shows us what the old trio is now up to. I would disagree with George because I thought it gave us some very different settings that we hadn’t seen before - in a very OT way. Yes, it starts on a desert planet, but not the same one. That was a friend’s biggest gripe about the PT - Tatooine again (it is in 5 out of the first 6 films). Here we get Jakku, site of an epic battle between the Rebels and the Empire. Then Takodana with Maz’s castle (and a cantina… not like GL didn’t give us one in AOTC). And sure the Resistance base feels a lot like the base on Yavin, but the planet is totally different (no jungle outside). And except for a couple of familiar characters, there isn’t a single familiar alien in the film. So GL was very wrong, because TFA did introduce a lot of new things to the Star Wars universe. But the story leaves a lot to be desired. It is all about the search for Luke - artificially prolonged for the entire film. Sure, Luke was going to steal the spotlight, but not being able to craft a story that can keep the new trio in the forefront really shows the lack of writing skill in the TFA writing team. The movie is a beautiful series of awesome scenes, but it lacks anything other than the search for Luke to hold it together. I think TLJ got in trouble for trying to take that poor start and get the story back on track.
And I think the the things they did change from GL’s original treatment (from what little we’ve heard that is reliable) was for the better. I fear he was revisiting his old scripts again and pulled things in that he had long ago abandoned and that is not a good thing to do for the big finale. I do hope that his concept for whatever force conflict IX was supposed to end with is close to what they are doing for TROS. But I think ultimately that this trilogy is the better for not following his treatment slavishly. They did admit that they treated it like any project and took the treatment and developed it from there. And if you look at GL’s own original treatment for Star Wars, the final film is much much different while still having a lot of similarities. The treatment to film process takes a good idea and makes it great. I just feel that TFA was derailed by the feelings of Luke coming on screen and taking over the story and their attempts to fix that. GL wasn’t in on that process so of course he was upset at the changes. I bet if he had been given the chance to go through their various drafts and see the story development that he would have been more accepting of the changes. But, he sold it outright and put Kennedy in charge so he clearly didn’t want any part of the development process. So it really is his own fault.