They're reinforcing gender stereotypes and thus creating a new culture where anyone who actually defies them anymore must not be a true man or woman. If you can cook dinner for your family, you're no longer allowed to be a man. If you have a career and earn more than your spouce, you're no longer allowed to be a woman. If you do both, you simply must be nonbinary!

And this is an insult to literally every woman and man in all of human history who worked to dismantle stereotypes and prove that women are capable of doing whatever a man can and that men are able to do whatever "womanly" things they like without being any less of a man. This nonbinary ideology is inherenlty sexist because its existence relies on the idea that a woman is inherenlty one way and a man is inherently another in far more than a genetic and reproductive sense