Throwing in my 2 cents into the fire because I can.
The entire age gap argument is largely meaningless because it doesn't ultimately stem from something rational. The kind of woman who would only date a man 20 or younger, and the kind of man who would only date someone under 20, don't have these preferences due to some innate "evolutionary biology" or whatever other cope they may conjur.
They get off on taking someone elses purity.
That's it, that's the entire appeal regardless of sex. A predatory tactic and a very vulgar display of soft power, sometimes of hard power. It's not about securing good offspring or maximising the amount of children you have. If that was the case, age while being a variable would not be so much of a corner stone in this line of thinking as it is. Believe it or not a lot of the people who end up pregnant at 16 aren't usually of the highest quality. And if you were looking for genetic quality you wouldn't be staring specifically at age, you'd take multiple other factors into account.
Now as a rule regardless men will generally go for a woman younger than them, either somewhat lower status or on the same societal level. Women will generally go for someone older than them, and either on the same societal level or higher status than them. These are general dating and courting preferences which repeat themselves throughout history. At the same time, for the vast majority of recorded history, people didn't stare themselves blind looking at ages as much as we are. And when they did, they were the exact sort of predatory person as those we find today.
It's true ultimately that women seem to be a lot less mature than men. At the same time, a lot of men are a lot less mature today than they should be. People have become intentionally infantilised, made mentally weak as to better be moulded in accordance with the whims of the elite. By different methods, true, people are kept away from avenues via which they would naturally grow and mature. The annihilation of marriage is one of the key methods used here, since motherhood seems to be the primary thing which drives women to mentally mature past 16 (even if they don't necessarily mature much further than that in my experience).
We'd all be better off if predatory people were punished for their desires and actions, rather than rewarded. More importantly: We'd be better off if we stopped rewarding them ourselves.
