Belz...
Fiend God
This looks like a swing and a miss to me. ‘We’ is just ‘the majority mainstream in the west’ opinion, and happened to be a very widely held belief.
It's not a belief. Just because you disagree with something does not make it a belief. And I'm not talking about the west. I'm talking about homo sapiens. In fact I said thousands but I could probably have said a billion and gotten away with it.
If you use the God metaphor, your statement would look like ‘We managed on the Catholic definition for a thousand years.
Sex is not a belief system. Nice try.
ETA even more: and I don’t get the impression that gender was something that many people ever really sat down and thought about throughout history.
Because it was clear that there were two sexes, and associated genders, with only a tiny number of people for whom that determination was harder. That has not changed. Our understanding has not changed, either. What we have here is people so dedicated to the idea of offending no one at no time that they are willing to accept counter-factual claims from said tiny number of people to upend the entire concept of sex and gender.