I suppose it depends on how much you respect the person who created the item or not and what they said was canon or not.
For example, Lucas never said Disney's creations were Canon, though he DID sell them the rights.
He DID say that the official canon items were...if I recall, the movies, the novels, and ironically, the radio dramas.
The order that they took precedence changed from time to time, originally the movies, but eventually whatever HE said was more true to his original vision (which actually in some ways at times were seen as the radio dramas with more of his original ideas, or the novels...it always seemed to be in flux. Lucas actually was quite wishy washy at times despite what some portray about him).
The EU, so derided by those who hate the older Star Wars or not really paid heed to by others was ALSO considered a form of Canon by Lucas. HOWEVER, he made it clear that it was not HIS Canon...it was NOT HIS universe. It happened in some other alternate universe.
Even so, he actually DICTATED some things that would happen there and nixed others, having some involvement and control over the entire EU. One of the more controversial things had to do with his decision on the death of a Anakin (named after Darth Vader Anakin) and the turn of an older brother called Jacen (who became, I think a Darth Krayt?). He had a LOT more control over some things that people attribute or like to think when they are in favor of the New Star Wars and loved the nixing of the EU.
So, it really depends on how much you respect creator's rights over their own creations.
We see variations on how much in favor people are or are not in regards to this.
For example, with Lord of the Rings some people are very adherent to JRRR Tolkien, others want artistic merit to be allowed.
Other items are much more foggy...who is considered the original creators of Marvel Comics or DC comics...especially as there are multiple story lines by multiple different authors. For Marvel is it always Stan Lee or is it Kirby or someone else?
If you respect Lucas and have it as HIS creation, than anything after the sale to Disney could not possibly be Canon, and several of the items while he still had full control are also not Canon.
If you are less respective, and rather are in favor of corporations rather than people, than anything and everything Disney says is Canon regardless of what Lucas may have said in the past.
And then there's a whole wide gulf of opinions and thoughts in between those two ideas.
As an occasional author myself, I tend to favor the individual Creator's rights in regards to Canon, but I also know that for many properties that was tossed away a LONG time ago in favor of corporation or business control (for example things such as Conan, Cthulhu, Tarzan and many other properties popular among the gaming community we are a part of).
