I began my writing journey on fanfiction.net after a fan page on wetpaint.com went down (wetpaint was my OG springboard for all things fanfics, then ff.net, livejournal and tumblr). I still visit it from time to time, reading fanfics that are not present on AO3.
What about you? Do you still visit ff?
Oh my. Now I’m intrigued. Haha. But you are so right. Ff.net has so many gems that are just not on AO3. I still crosspost though, if only because I still have some readers there. But I do notice that activity has decreased over the years.