Gender as a thing does not have an ontologically distinct like a rock does. I don't buy into extreme skepticism, so for me the rock exists regardless of my own mental states. However, the same cannot be said for gender. Gender as a thing depends entirely on human society for its existence & its properties.

Compare gender to a concept such as beauty. Beauty is less likely to be entirely dependent on human society for its own existence. My intuition tells me that I could more easily explain why this particular Roman temple is pretty to an alien from Alpha Centauri than I could explain why my humans society teaches women that they must maintain a youthful appearance beyond what is healthy in order to be seen as high-value women.

I draw upon Alyson Escalante's Gender Nihilism for my thoughts on gender. Those words guided me throughout the period where I lived as a nonbinary person. While I'm not sure I stand by the negationist stance anymore (Escalante has moved past it & offers a solid approach beyond refusal), I still believe that gender is not the most stable concept that human beings have devised.

Gender norms are so malleable, & they are victims of the existing power structures. They apply in one situation then in another they are suspended for arbitrary reasons. In one century, men wear pink, women wear blue; in another, men wear blue, women wear pink.

I agree with Escalante's essay on a materialist conception of gender. In addition to the ideological component of gender (the metaphysics & epistemology), the economic & power structures are also relevant (I hinted at this before). Women do not already exist as a category; rather, what is already existing is reinterpreted  according to the needs of patriarchy as that system evolves over time.

TL;DR gender as an essence is dumb & bad.