I think the main things that are holding us back from this vision at the moment is reproduction and the quality of gender affirming care. You still need to have male and female to have children and for now we can't change which you belong to. If we could do like the Culture and have people that father one child and give birth to another this would all be a lot simpler.

I actually think that without gender roles and norms many people would end up presenting as what we would consider non-binary today. I don't think it's actually true that male and female people actually behave like men and women inherently for the most part. I think the kinds of behaviour that's actually determined by chromosomes and hormones is fairly limited.