Working within the limitations of the shared world generally made the writing easier, because I didn't have to invent any of the characters or background, which is usually the hardest part.
Some of my ideas were shot down by Lucasfilm because they stepped on territory that has been reserved for the movies. I didn't have a problem with that.
It's a tough job to tell a story when the audience already knows the ending, and the ending is bleak.
That's why editors and publishers will never be obsolete: a reader wants someone with taste and authority to point them in the direction of the good stuff, and to keep the awful stuff away from their door.