For those that say George Lucas didn't care for the EU.
https://youtube.com/watch?v=QWUzWuRZjHw
He approved it for the sake of drumming up anticipation for the special editions and prequel trilogy and took a handful of things from it (the name "Coruscant" for example), but he admittedly never really respected it, and I say this as a post-ROTJ EU fan. I think he had more direct involvement with Shadows of the Empire admittedly.
The real issue is there wasn't a perceived obligation to follow EU canon when he made the prequels. For example, the clone wars as depicted in Attack of the Clones and subsequent media is different from what The Thrawn Trilogy implied, and what it implied reflected earlier drafts of what Lucas conceived the clone wars as before he changed his mind. Later retcons "fixed" this and made it somewhat make sense, but the fact they even
had to make said retcons highlights the whole issue. I don't even per say think the Clone Wars as eventually conceived was a bad idea, but I dislike that it contradicts arguably the best Star Wars novels retcons notwithstanding.
The most egregious contradictions however come from The Clone Wars cartoon (CGI one, not the Tartakovsky one), in fact it was in 2009 that I realized the EU was kinda fucked because of this cartoon. Specifically I am thinking of the infamous Ryloth incident. Basically, in the old EU the planet Ryloth was tidally locked, which means one side is always daytime, the other nighttime, and the Twi'Leks live in the twilight zone and huge aspects of their culture are based around this unique aspect of their planet. The Clone Wars had a bunch of episodes taking place on Ryloth and they just depicted the planet with a normal day-night cycle. This is particularly egregious because it was just negligence—they could have easily told the story they wanted to tell whilst integrating that unique aspect of the planet into said story which would have made that story arc even more interesting, but instead they decided to be oblivious. To be honest you're basically obligated to retroactively consider that entire cartoon Disney canon because of the sheer amount of contradictions (which it sorta is; besides the 6 films it's the only other media that remained canon in the Disney continuity, and they even made another season in 2020).
I actually do like some of Lucas' ideas, but this whole argument-from-authority idea of canon pertaining to the series' creator isn't really a consistent precedent with media. Even if we discount recent shitty Star Trek or the JJ Abrams films, some of Star Trek The Next Generation and all of Deep Space 9, Voyager, and Enterprise were made after Gene Roddenberry died. There's also the fact many episodes of Star Trek prior to his death weren't written by him, and it's even generally agreed he would have hated the main defining story arc of Deep Space 9 as it went against his idea of Star Trek. Despite this, if someone came along and said all of this wasn't canon to Star Trek because Gene Roddenberry didn't write it or even likely would have hated some of it, you'd think they were insane. This is why I don't really care. George Lucas apparently wanted Star Wars to be kids movies even though the first three films sans Ewoks qualify as general audience films (especially Empire). I feel safe in saying the juvenile stuff detracts; the best "kid's media" is general audiences media. Boys like Star Wars because it has space ships and lasers and shit, they don't need Ewoks or Jar Jar to like it. You add tonally off baby stuff and the film just ages poorly with the viewers. It was always a bad idea.
