Uhh, Kathleen Kennedy said there wasn't any reference material for them to work with.

Are you opposing the viewpoint of a woman, bigot? For the love of science you better not be mansplaining to her.

Some of the books sucked, but there was a lot of great material in the EU that they unceremoniously removed from canon.

A Thrawn trilogy would have been great, but they waited too long to make it. All the major characters were too old. It should been made a few years after Revenge of the Sith.