This is still in Early Access and Larian said this might last a year. The romance that we have currently available in the game is just a taste to give us an idea of what they are doing. That's why when your character has sex it says "Under Construction" because they are still working on it. If you feel the romance is rushed, keep in mind that the game is not finished yet. When you got the Early Access, it tells you to give Larian feedback so they know what they should add or work on and that's what these forums are for.
I think you're right. It seems like the only romance that is really complete is the one with the drow lady, which makes sense. She is probably not gonna have any meaningful role later in the game so they could finish her romance for early access.
