The same fictional universe that gave us Khan, also gave us the characters of Julian Bashir, Una Chin-Riley, and La'an Noonien-Singh all having to deal with a socity that, in universe, had faced this as a history lesson rather than as a fantasy.
Were the Ferengi a warning against American capitalism? The Bajorans a promotion of terrorist tactics to expell imperialist colonisers? The Changelings a warning against… plastic surgery?
Fiction is about interesting tales, not about realistic forecasts — TOS Khan was supposed to have ruled in the Eugenics Wars of the 1990s.