There has been a Star Wars Universe for many years prior to the Disney takeover. While spinoff movies and tv series have been added to the books and comics of the much beloved EU of old
People have made much of the fact that the originals were based on archetypes, stock characters, and the hero’s journey, which is absolutely true.
The OT is very much Luke’s story, with Han/Leia and the rebellion forming a subplot and background. One of the reasons ROTJ feels like the weakest film is because there’s nothing left to Han and Leia’s story and the rebellion storyline mostly copies what we saw in ANH, although I don’t think that bit is quite as derivative as some people make out.
ANH, ESB, and ROTJ all have Luke’s hero’s journey at the core. I think that once it stops being Luke’s story, SW starts to falter. In contrast, something like Star Trek can be remade in numerous forms because it’s far more interested in building a universe and telling episodic stories than it is in protagonists and telling single stories. While SW was very much about Luke, Star Trek was never that much about Kirk or Spock.
Going to compare to Harry Potter again since I think it’s strikingly similar to Star Wars. People love aspects of Harry Potter’s world, just like they enjoy aspects of what they see in Star Wars. Like Star Wars, HP took familiar concepts and worked them into something new.
But nothing outside of the original series seems to carry much weight because Harry Potter is about Harry Potter, not his world. It’s a bildungsroman as much as anything else. The heart of the book is Harry growing up, and the central story is his own version of the heroes journey, which follows pretty similar beats to Luke’s. Now they’re trying to make new Potter movies without the actual thing that made the series popular and unique. Spells and magic were the background. Having them without the core is like making dinner using only the spice rack. I think the same thing is happening with Star Wars.