Visual communication is incredibly important. I think I’ve had sex in the dark like… less than 1% of the time. You’re either trying to keep up a rapport to maintain their enthusiastic future availability or emotionally invested and attempting to maintain reciprocity. Unless you’re both fairly charming and willing to lower your standards, lights are worth keeping on. Sex is just as intrinsically tied to the social contract as anything else.
That said, yeah, marry for personality imo.