I think the main reason is that the real story is about Rey and her mysterious origins. The starkiller base, when you think about it, is actually very insignificant to the plot it’s easily forgettable. It’s a MacGuffin in the truest sense of the word.
Well the main story in the original is about Luke and his origins. If you take the Starkiller base out of VII and Death Star out of IV then they’re still the same story. A lowly young adult on a desert planet stumbles across a droid carrying important information, Stormtroopers are sent to the desert planet to retrieve the droid, and so they go off on a grand space adventure leaving on the “what a piece of Junk” Falcon. Darth Vader/Kylo Ren interrogates people and kills them afterward, etc, it’s a straight remake with a few throwbacks to the sequels thrown in.
It doesn’t take the Star Wars story anywhere, by the end of the film everything we just saw was just action with no advancement in the story. It’s a bit like Matrix Reloaded compared to The Matrix in regards to the focus on action. And by taking Rey to Luke at the end of the movie the only difference between IV and VII is that VII ends at the beginning of the second act of V instead of at the end of the third act of IV.
It seems pretty clear that the plot on paper is just a blatant carbon copy of the original movie. Sure, there are some tangential differences, but the essential elements of the movie are identical to the first film.
So knowing this, how can anyone still say this is a good movie?
Yes it is. I guess it’s intended to serve as a series “reboot”, but just like Jurassic World for example there’s no originality to it at all, it’s just a straight remake, made into a marvel-style non-stop action movie. It’s good in its own way, but a wholly unnecessary sequel really. I wouldn’t really say it’s a good “Star Wars” movie though, as a standalone film it’s fine, but slotting into the SW narrative it’s pretty mediocre really.