Real world romance with no historical or magical obstacles
Contemporary romance is one of the hardest genres to pull off. Readers know a "happily ever after" is coming, unlike in other genres where the ending isn't guaranteed, which makes believable plot machinations that aren't too predictable or too stupid hard. It can be hard to generate conflict between characters that's believable and keeps you rooting for the ending. With historical or fantastical romance, writers can generate obstacles but when a book takes place in a recognizable world, the author has to make the conflict truly believable for the reader to care.