Gender is a social construct often upheld by patriarchal societal standards. The being of a man or a woman comes with many societal expectations, and quite a lot of people don’t agree with that.

Do you mean "gender role"?

Patriarchal societies often have different expectations for people of different biological sex. A Confucian society would expect a man to follow the Son of Heaven and a woman to follow her father or husband. This is gender role, and gender equality means the abolishment of gender roles.

I don't think I can agree with conflating the concept of "gender" and "gender role".

Now, I only want to comment on the gender aspect as I am sure that you, master observer that you are, can acknowledge stuff like intersex people existing, who are born with both sets of genitals for example.

After some thought, I think I see your point. If one considers intersex a biological sex then their true gender should be separate from their sex. Is that what you were trying to convey?

Now, gender as we know it now has evolved in capitalist societies

Please tell me what the concept of gender was like in other societies. Be it Medieval Europe or Imperial China or whatever society you are familiar with.

Non binary people, for example, have been around since the beginning of mankind and have even been acknowledged by historic societies.

Please provide me documents. I may take my time to research them.