if we did live in a genderless world where straight non-trans men could wear dresses and have flowing hair and wear makeup would straight women still fancy them?
I would finally be able to find the man of my dreams, then. Well, minus the make up, perhaps.
Though Johnny Depp did look rather nice with all that eyeliner ...
Heterosexuality functions without gender performance. Animals don't perform gender. A male dog will run after a female dog in heat no matter how groomed her fur is.
And for humans, what is considered "masculine" is very different depending on culture.
Without performing gender, humans might have a bit of a problem to find out what sex someone is as the human nose is so degenerated, but that's really the only practical purpose gender performance serves - help people find out if that attractive person there is of their preferred sex.
However, we are an intelligent species and have other ways of finding out. (Pratchett's Discworld dwarves have no gender, and for them, the first step in romance is to very tactfully find out what sex the other person is ... I see no reason why this principle couldn't be applied in the real world. After all, it is rather rare that you can't see it immediately, anyway.)
That whole "But you should be attracted to personality" thing is nonsense. Men who can't live with the fact that lesbians don't like penis have a rather unattractive personality, too.(Which might be part of the reason why they're singles ...)