The issue with this is that making a Star Wars movie based on a comic book or novel is that only a small subsection of the general audience has actually read whatever comic book or novel that the film was based on. Lucasfilm also couldn’t adapt, for example, the Heir to the Empire trilogy of novels by Timothy Zahn, who founded the EU, for three major reasons:
The first EU book was published all the way back in 1991, the year I was born. (I’m 31 years old currently.) Disney purchased Lucasfilm in 2012, and didn’t release Star Wars: The Force Awakens until December 2015. By that time, the original cast members that the original Legends EU trilogy primarily focused on - Mark Hamill, Harrison Ford, and Carrie Fisher - were too old to reprise their roles as Luke Skywalker, Han Solo, and Princess Leia. However, Disney managed to fit them into the sequels that we got in the 2010s.
As the three main original cast members aforementioned were too old to reprise their original roles in an adaptation of Heir to the Empire by Timothy Zahn, this would have required a much-more-controversial recasting of the main three leads of the original trilogy with new, younger actors. Recasting is already deeply controversial in the Star Wars fandom, with Solo: A Star Wars Story - the testing ground for recasting - being widely seen as a box office bomb or disappointment. Disney decided not to recast.
The EU itself did not have a single director and “vision” - that of George Lucas - but rather, a wide array and hodgepodge of different books, written by different authors, sometimes with their “visions” for what the story and direction of Star Wars should be directly conflicting with one another. There was at least one notable feud between two EU authors, for example, when it came to romance in the EU books; and even a feud between Timothy Zahn, the most popular EU author, and George Lucas himself over whether or not Luke Skywalker should fall in love, get married, and have children. (Lucas envisioned Luke as a hermit, whereas Zahn envisioned Luke as having a wife and children.) This was one of the biggest reasons why Disney decided to scrap the EU from 1991 to 2012 and start over from scratch, as they sought to create “one single, unified, consistent canon and vision for all new Star Wars books going forwards”. To this end, the Lucasfilm Story Group was founded, but discrepancies still happened occasionally.
The issue with this is that making a Star Wars movie based on a comic book or novel is that only a small subsection of the general audience has actually read whatever comic book or novel that the film was based on. Lucasfilm also couldn’t adapt, for example, the Heir to the Empire trilogy of novels by Timothy Zahn, who founded the EU, for three major reasons: