Hmm, to expand a bit on my oppinion.
First of all, I think, in principle, that it belongs in an open world game, that prides itself on player freedom. However it shouldn't be in there, at any cost.
If it's reduced to the following: Picking a dialogue option and/or "buying" someone and/or anyone.
Then: Thank you, but no thank you.
More right, though not perfect to everyone is this:
1. Can't get everyone. Only the "bigger" characters are romance options.
2. Not everyone will match with you. The characters will like you, dislike you depending on your behaviour, reputation, six, sixuality, age and what not... A realistic pick of the most wellknown friendzoned/nemesis arguments.
3. You will have to work at it. Through dialogue and possibly miniquests, you will have to get to know the character and the character will have to know you. Time and energy needs to be invested (not the entire game), but effort needs to be made.
4. Romance should be an easily recognized option, that you actively and explicitly choose.Don't wanna end up in a dialogue tree, where you suddenly think: "Wait, why am I apparently breaking up with this person. When the hell were we dating? Am I gonna piss X off now? AAAAGH"
5. I don't mind getting shown (don't NEED it either), to some degree, bedroom gymnastics, but again this should be an easily recognized option, that you actively have to select. Don't mind that it's not hyperrealistic.
...
I think this might be the best possible way of putting romance in the game, given current technical limitations and allowing for the most freedom to most players. Possibly being an additional layer on top of something like companion loyalty. Where eg. companions fight with you to the death, for well not really any particular reason or personal attachment.