I'd like to point out that romantic and/or sexual relationships do tend to work better if the people are attracted to each other. Appearance plays a role in many peoples' attractiveness functions. It's difficult or perhaps impossible to intentionally change one's attractiveness function, so this doesn't indicate a personality flaw or moral failure. Optimizing for attractive appearance at the expense of other things might be a mistake*, but most people would do best if they at least satisfice for it.

I'm sure some people do weight appearance for signaling value when choosing a partner, but I don't think it could be the only reason. Most people I have talked to about this say that appearances influence how attractive they find someone, and they don't all agree on what they find attractive, even within the same social circles.

*I know that the chemical things that happen in the brain when a person is in love can make them like things about the other person that they would ordinarily be bothered by. I remember several times when I started finding a person much more visually attractive than I had when I'd first met them when other things changed (getting to know them better, etc.), and also finding strangers who looked like them slightly attractive. My attraction function is really weird, though, so this isn't very strong evidence unless I see other people reporting the same experience.