Honestly, my desire for prompt writing and/or claiming mainly revolves around saying "nobody's ever written this pairing and I think it might be fun, anyone wanna give it a whirl?" And the AO3 format doesn't really support that, does it? Prompts on Tumblr and DW anon prompt memes still work okay for me, although it depends a lot on the culture of the specific fandom. I don't know what causes certain tropes or plots to take off in certain fandoms, but it's affected my fandom participation probably more than anything.