Well, undead tend not to have much in the way of biology, either.
Oozes are literal collections of slime that don't even reproduce and merely emerge through spontaneous generation. Even the robots are arguably more sexual than that.
I mean, sure, reproduction is out of the question, but Thist did learn enough social skills to be more sexual than Data.
I think you're conflating sex with romance here. I'm not doubting Thist's ability to form relationships, but all oozes are intrinsically asexual. No amount of social skill will change that.