I'm so picky about fics because I want them to be very realistic but also better than realism at the same time. The best possible version of reality, I guess? Because all my favorite fics have some distinct element of imperfection/idiosyncrasy. There needs to be fumbling or awkwardness or apprehension or miscommunication or something. Or a character has a strange quirk or kink that's weird but somehow still hot. I want it to be like really good low-budget amateur porn, not glossy overdone pro studio porn. It takes me out of the story when the characters are all impossibly fit with gigantic cocks that get instantly hard and the sex is always the pinnacle of perfection.