Is monogamy a feature of advanced cultures that emphasize a person’s individuality? I mean cultures that treat someone as person and not as an anonymous part of something else, e.g. nature or a tribe.
The standards for inter-gender relations appear to be a deep cultural thing. As such, it tends to go hand-in-hand with language family, which means the root of the differences probably go back to a time when pretty much everyone was operating in the Mesolithic ("Stone Age")
Indo-European cultures tend to a strict one-to-one marriage, with offspring from pairings outside that system not being considered legitimate.
Afro-asiatic cultures tend to a one (male) to many marriage system, where male offspring are accorded status by birth order (regardless of mother).
Chinese cultures have a middle-ground between these two poles, where a man can have more than one wife, but the senior wife and her offspring have elevated status.
Tibetian culture traditionally went instead toward Polyandry (or in rare cases involving no male heirs polygamy), with all male children having equal status.
Mongolian culture had strict binary marriage, like the Indo-Europeans, but all male children got close to equal status, with the youngest being slightly advantaged, getting undividable things like the father's title and actual tent location. The Ancient Mongolians would probably claim they were indeed more "advanced" than their Chinese neighbors, but I suspect the Chinese would strongly disagree. In writing.
I'd caution anyone against picking out a cultural feature that happened to be used by the winners of the Age of Imperialism and trying to find a reason why that one is somehow better. This isn't anything more than Survivorship Bias.