[a fool in paradise]

Luke and Leia were originally written as a couple until it was later decided they’d be brother and sister. #AwkwardMoments

[ClearBlueSky]

You're right-the original story was a romantic triangle-a-la-Gone With the Wind-hence the similar poster for Empire. It made more sense. Veering away AFTER the on-screen dynamic was established made everything after look stupid. Lucas didn't care about continuity or how it made things look in retrospect, according to Gary Kurtz. Any 'ick' factor was due to Lucas getting to ROTJ and just wanting a quick, easy way to wrap up a dynamic he didn't want to resolve logically.Even as late as Empire the promotional pics had Hamill and Fisher appearing 'couple' like, especially in promo pics for the foreign press.
By ROTJ Lucas had become what he had hated, a corporation. His focus became merchandising at the expense of storytelling. Empire was great because the director fought Lucas who admitted later that it was 'a better picture than I wanted to make.' Imagine that-he wanted worse, less...explains Ewoks and the Prequels, eh?