Just about every Star Wars fan is guilty of it, including me, but it’s time to retire the term “canon”. Fans obsess over what is or isn’t canon, but since the reset back in 2014 that really isn’t needed.
Everything prior to 2014 that isn’t one of the movies or part of The Clone Wars was given the “Legends” banner not so much because they weren’t “canon”, but because they may have had something that would contradict something else in the newer stuff being produced.
That’s the entire purpose of the mythical and nebulous “canon” Star Wars fans obsess over. What they see as making something “official” isn’t exactly the purpose of the “canon”. It’s really just to determine if something would affect the story of some other Star Wars thing, be it a book, comic, TV episode, or movie.
Established would be a better way to think of events or characters in the “canon”.
A great example is Rogue One. When John Knoll first pitched the concept he asked if the Death Star plans heist was ever done before. In Legends it was done multiple contradictory times, but since the 2014 reset it wasn’t officially established in the time line. So Rogue One established the events of how the Death Star plans were stolen and that would affect other events being chronicled in all other mediums of Star Wars.
“Is this canon?” “That’s not canon!” are dumb arguments with how Star Wars is being handled now. Prior to this season of Rebels, the existence of Thrawn wasn’t established in the official timeline of Star Wars and now he is.
Absolutely anything from Legends has the potential to become established as official, as long as it isn’t something that would contradict something else or break the established rules of the universe that George Lucas created. Thrawn’s Ysalamiri and the idea of “Gray” Jedi are two Legends concepts that would break those rules, thus they wouldn’t work in the established Star Wars universe.
So when Lucasfilm decides to bring something from Legends into the Star Wars universe they aren’t so much making it canon, but establishing a new building block upon with all other Star Wars stories can build upon and use.
Thus it’s time to stop thinking of Star Wars canon as some kind of monolithic gate that exists just to make fans argue. It’s time to retire the term.