“ If this were true, then there’d be absolutely no need for diversity. If we are all uniform, then we are all interchangeable.”
You misunderstand ethnicity and acculturation, which makes people not interchangeable.
You misunderstand historical and present prejudices against skin color, despite race being a social construct, and you misunderstand historical prejudice against women, despite gender being something not tied to biological sex.
People aren’t interchangeable. People who deserve seats in the government, or business leadership, or scientific leadership, aren’t there because of a historic prejudice which depends on social constructs to exist and flourishes because the social constructs were set up to depict certain people certain ways.