That’s not the case in my western country but sure, hit that scarecrow. I personally know underage people dating 25-ish people.
What is frowned upon is people in completely different levels of maturity creating a tremendous imbalance, and usually abuse. DiCaprio dating teens is not a “we stand on an equal footing and love each other” kind of thing, is a “I’m famous and will use this fact to mess with teenagers”.
An elderly hardly has a healthy relationship with a teenager, and this is particularly true for arranged marriages.
This western civilization thing of your already had that in the past. We stopped doing that rather recently as we figured it creates more trouble than not. Let’s not pretend that “western” is some sort of axiom that just appeared and not the product of the evolution of some society. Just like eastern societies have such evolutions in some aspects. For example some eastern civilisations figured that clean spaces are better and so they try real hard to try to keep them that way. Of course you’re free to argue that this cleanliness is not needed so it is a purely subjective thing of these societies and not necessarily better, but sociologists night disagree.
As for “ok if the victim preforms the deed”, that’s irrelevant. The same criteria applies. Promoting healthier relationships promotes a healthier society. If some 14/yo teenager is obsessed with dating way older men for whatever reason, chances are people are going to judge it, legal or not, no matter the society.