One thing I've recently discovered I am effectively incapable of writing well is romance that involves a woman and/or is clean. In my (straight and cisfemale) dating experience, you have to talk about sex, and trying to write romance without that (at least the conversation, if nothing else) just feels painfully unrealistic to me. Even if you remove the clean qualifier, I have a terrible time writing anything romantic that involves a woman. I think I feel like anyone reading it will assume it's somehow inspired by my own experience, and that makes me phenomenally uncomfortable, even though I share my own dating stories freely and with excitement. It just feels weirdly exposing. Give me a gay couple? Now I can get somewhere.
So there's my unpopular opinion for the thread.
Of course some other things mentioned here I wouldn't write, but there's no point in repeating what others have said. I would have a very hard time with fantasy from a self-motivation point of view, but for enough money I'd find a way.