Great post @BarrackerBarmer
I have always been a gender critical feminist since a child as I witnessed first hand the violent abuse and coercive control inflicted on my mother by my father.
My father was an alcoholic who, although a bit of a polymath and great at his chosen vocation, ended living in a caravan on a farm.
When my mother tried to take over the mortgage payments (as my father was incapable of paying them regularly) she was told at first she couldn't because she was female.
She did everything- DIY, working, paying the mortgage, renting out rooms to lodgers, bringing up her children. I knew all this men are innately better at x, y or z was bollocks.
So, although my analysis of what crap gender is started young it was as a result of somewhat precocious experience.
Even still, although I saw that the world was structured in favour of men as a young woman I still harboured the idea that I would overcome it because I was special!
Fundamentally, my view is that it is experience that makes you gender critical and that the older you get the more sexism and discrimination on the basis of your biology you experience.