The retcon was totally necessary.
There are several excellent stories from the EU, particularly Kotor, Thrawn, and some other novels, the original Clone Wars and Dark Horse Comics were solid as well. Swtor for the most part has had great storytelling as well. (Although they totally fucked up Revan as a character.)
However, there were to many contradictions and bad stories, not to mention the fact that while the force could be awesome in the EU, had turned into like a D&D spell book. The concept of the force was raped by the Force Unleashed. The force works because it is powerful yet not all powerful. I don't think we'll be seeing any Starkillers in the continuity soon, thank god for that. As cool as massive shockwaves and mastering both sides of the force are, it just doesn't work with the original concept of the force.
The franchise needs to concise storytelling. Let's face it, most of the material (OT, RoTS, Clone Wars and yes, even Rebels are fantastic.) not to mention the new comics and adult novels are amazing.
All of the unnecessary garbage of the EU is being dropped, and it's the next best thing to retconning the prequels and Lucas's stupid remakes to the original movies.
As fans we should be thankful for the fact that Lucas for the most part is out of the picture and that we will get a coherent Star Wars universe. Disney knows how to make movies, just look at the Marvel cinematic continuity.
Finally, there is a lot of EU material that is being reworked into canon.
For example:
The Old Republic
Planets and species such as Anaxes and Chiss
The Sith Homeworld (if we can get over the fact it was changed to Moraband, fuck you Lucas)
Etc etc
The next generation of writers is gonna have a field day, the retcon is creating opportunities.
besides, the Vong was a $hit concept, seriously, a snake can withstand a lightsaber?
