What is significant about fan fiction is that it often spins the kind of stories that showrunners wouldn’t think to tell, because fanficcers often come from a different demographic. The discomfort seems to be not that the shows are being reinterpreted by fans, but that they are being reinterpreted by the wrong sorts of fans – women, people of colour, queer kids, horny teenagers, people who are not professional writers, people who actually care about continuity (sorry). The proper way for cultural mythmaking to progress, it is implied, is for privileged men to recreate the works of privileged men from previous generations whilst everyone else listens quietly. That’s how it’s always been done. That’s how it should be done in the future, whatever Tumblr says.
But time can be rewritten. Myths can bend and change. Something new and exciting is happening in the world of storytelling, and fans are an important part of it.