I don't think that's universally true. Being attractive certainly can help make good impressions easier (and I've known insufferable people coast by on good looks too) but I don't think it's the be-all or end-all of romance.
I've known women that have broken up with or turned down attractive men because they didn't enjoy talking with them, or had different political views, or wanted to have/not have children. Conversely, I've known men that didn't exactly look like movie stars end up in relationships with nice-looking women too. That's not even considering same-sex attraction either. Heck, I've turned people down to date less physically-attractive people in the past too.
I've known women that have broken up with or turned down attractive men because they didn't enjoy talking with them, or had different political views, or wanted to have/not have children. Conversely, I've known men that didn't exactly look like movie stars end up in relationships with nice-looking women too. That's not even considering same-sex attraction either. Heck, I've turned people down to date less physically-attractive people in the past too.