Now keep in mind this is an opinion, a rather strong one. But I hate how almost every supernatural romance I am asked to read shares the same basic setup as your typical romance novel that doesn't have a single supernatural element in it.
It's so bad it gets to the point you can easily forget that the supernatural lead (almost always a male mind you) can easily be subbed in for a human and nothing about the story would change. That's how little the supernatural element really is in these stories.
None of these authors bother to dig into how perverse some of these joinings could be. Or how they walk the fine lines of actual love, lust and obsession. How dark and dangerous it would actually be. They do venture to the meat of the relationship instead they throw another supernatural creature into the mix for a love triangle.
The fact that human is falling in love with something that is normally considered a monster should be the heart of the story. In truth them having feelings for said monster character speaks in volumes about the characters sanity or lack there of. How deprived they might even be. When someone loves someone that kills and might even eat people for a living, they are not completely okay in the head. Loving those kind of people doesn't make them understanding.
However, that would mean the main supernatural character would have to act like they are supposed to even a little bit. Like a vampire actually feeding on people and not deer. A demon still wanting to give into his urges and doing so.
Supernatural Romance should be what Dark Fantasy is to Fantasy. I am not saying you shouldn't have a happy ending or a silver lining, but for fuck sake make those characters work for it other than some boring ass love triangle nonsense. Show us the readers that a monster might merit being loved.