I don't think it's complicated.
World Health Organisation definition of gender:
"Gender refers to the characteristics of women, men, girls and boys that are socially constructed. This includes norms, behaviours and roles associated with being a woman, man, girl or boy, as well as relationships with each other. As a social construct, gender varies from society to society and can change over time."
So gender would be the expectation that a woman should not receive an education or vote, that pink was a strong masculine colour (light red), but is now a soft effeminate colour, that soccer is a game for women and young boys in the US, but a man's game in the rest of the world, that women can wear men's clothes, but man can't wear dresses - unless they are in the church.
If you think this is worthy of criticism you are gender critical, and it follows that you think identifying with a gender is bonkers.