Last year's Star Wars: The Rise of Skywalker was a relatively middling end to an already mixed Sequel Trilogy, but if it showed us one thing, it's that a straight adaptation of the EU would not have been a good thing. Despite some powerful performances by the central cast, the last film in the Skywalker saga was heavily criticized for a plot that felt more like a video game fetch-quest than an engaging story, as well as relying too heavily on perceived fan-service. The final result was a movie that leaves more questions than answers, lots of which have been resolved in supplemental material and additional reading that leaves the movie feeling like a homework assignment.
Conversely, the Star Wars EU felt like the exact opposite of homework. Back in the dark ages of the Star Wars content drought (1985-1991), the formation of the Extended Universe was like a breath of life for fans. What started out as two major projects that continued the story of Leia, Han, and Luke quickly escalated into a living, breathing web of storytelling that fleshed out never-before-seen corners of the Star Wars universe. Not only were fans finding out what happened to their favorite characters post-Return of the Jedi, but they were also discovering information about the origins of the Sith and the many intergalactic wars that ravaged the galaxy.
When Disney de-canonized the EU (technically it was never actually canon in the first place) back in 2014, many fans saw this as a slight against the legacy of the Expanded Universe and all the stories provided by it. However, after seeing The Rise of Skywalker, it's evident that a straight adaptation of the EU would never have been as good as Star Wars fans assume.
For starters, one of the major problems with The Rise of Skywalker was just how hard the movie leaned into the expected fan conventions. With the mixed reception to The Last Jedi's subversive narrative and challenging character writing, a vocal faction of the fanbase demanded a return to form for Disney's Star Wars films. Rather than stick to their guns and go with another equally challenging film (something Colin Trevorrow's original Episode IX script attempted to do), Disney and J.J. Abrams instead doubled down on fan service to widen the movie's appeal.
However, a lot of the movie's fan service is merely plot devices repurposed from the EU, such as Palpatine's return and his usage of cloning. While there are several plot elements in the Sequel Trilogy that are borrowed from the EU, The Rise of Skywalker leans into it the heaviest. By simply re-using these plot points on-screen, audiences can see just how implausible some of the writing in the EU truly was. The Expanded Universe lasted for over 20 years, and in that time fans got to experience a lot of great material, but also a lot of ridiculous and unnecessary material as well.
Of course, in the format of a constantly expanding literary universe, that kind of absurdity is given a pass. For every story about Chewbacca running into Indiana Jones, the EU also gave us classic titles like Heir to the Empire and the Jedi Academy series. As a whole, it's difficult to call the entirety of the Expanded Universe objectively "good" or "bad," just expansive. It's easier to sift through the bad when there's a wealth of content to plumb through and there's a chance you might stumble upon a diamond. However, as Star Wars: The Rise of Skywalker showed us, the kind of storytelling that was prevalent in the Expanded Universe worked because of the medium that the EU was being told in, and even though it was a difficult choice, Disney made the right one in not adapting the Expanded Universe into new canon and starting over from the ground up instead.