It was born out of marginalized groups such as women, people of colour, and members of the queer community deciding to take the stories that had been aimed at a largely male, white, heterosexual audience and inverting them into something they could enjoy and relate to. On the other hand, you have the roots of fanfic. This makes it incredibly easy for anyone at all to find and read fanfic.
On the one hand, you have sites like AO3 and realities like widespread high speed internet access being more and more accessible to larger and larger groups of people. It’s such an interesting dichotomy to think about! They were talking about how fanfic is becoming more and more mainstream while still remaining largely transgressive. I wish I could find them again (or that I’d just saved their post at the time) because I think they made a lot of sense. Somewhere in my notes in the last few days I saw someone add some tags that I’ve been thinking about ever since.