See, I need my short smut to have enough characterization for me to understand why the characters are into it, so that's the one thing where I actually do tend to stick to fandoms I know! Also if it's a new fandom I'll get distracted from the smut trying to learn the fandom. (It does limit what I can read, sadly, because yeah, it needs to be the right kink and the right fandom and the right characterization and that's a tough call sometimes.)