5. The Entire Expanded Universe
When Disney announced that they were basically choosing to ignore the entirety of the Expanded Universe as non-canonical, they followed firmly in the footsteps of their predecessor, who was always committed to his manifesto that he never wanted his vision to be "muddied." Lucas always made it plainly clear that he had no real commitment to the EU; he was the creator, and the films were his, and as such he set those films and The Clone Wars series as the canon. As the official statement on the EU stated: "these stories are the immovable objects of Star Wars history, the characters and events to which all other tales must align." It is no real surprise that Lucas didn't endorse the work of others expanding on his original central idea, considering the potential for some of that material to surpass his own, but it seems rather arrogant for that whole library of material to be deemed expendable.