The EU makes the point that the Sith were an ancient galactic space-faring species. The Sith were among the species brought to the planet Tython in the Dawn of the Jedi comic series. Where did the term "Dark Lord of the Sith" originate and what does this term refer to? This term implies there is a group called the Sith and they have powerful overlords. This term goes back to the novelization of A New Hope. The blueprint for the Expanded Universe is right there in the novelization (1976) and film (1977) for A New Hope. Lucas could bang his head on the ceiling all day and mince words in every interview post-1999, but -- there needs to still be a war between Jedi and Sith, many wars, as implied by the blueprints he created when he was younger. My view is that Lucas turned over those eras to other people by licensing out the timeline. The EU was sufficiently cohesive to provide revelations on the back story for the Sith and Jedi. The EU is still in print and impacts the direction of the current line of stories. Sometimes we see direct references to the EU. The revelations of the EU canon cannot be undone. It is too late. We have the option of joining canons or reading one of the two in exclusion of the other.