Monogamy is not a "myth" any more than vegetarianism is.
Most of what we have is actually serial-monogamy, which is technically a form of polyamory, if you have many sexual relationships throughout your life. The idea is that you are exclusive to one at a time, but you break up and start new relationships.
If you are divorced and remarried, that is polygamy, since technically -gamy refers to marriage. But monogamy is also used in place of "monoamory" or "monosexuality".
Humans are not biologically predisposed to be monogamous (neither men nor women), but have adopted monogamy to deal with current civilization and culture, and it brings a good balance.
Hominids have been around for millions of years, and modern humans 200,000. During most of that time, we were polyamorous hunter-gatherers. Then 10,000 years ago, we switched to a lot of polygyny (1 man, multiple women), and now serial monogamy has become the norm.
As hunter gatherers, we were very mobile, so people could not hoarde resources and claimed little or no ownership of anything. Certainly not each other. We have a very high sensitivity to injustice, so we lived under what is called "fierce egalitarianism", where people would actually kick others out for trying to hoarde resources or power.
With agriculture, food was actually a major problem before it got better. As such we quickly became terretorial, and claimed ownership of things, including children. We had to establish which man would be responsible for which child, so you start seeing men "own" women by exchanging resources for exclusive sexual access. As such, men would hoarde more power and resources, and women would have to practice "hypergamy", where they would marry into their economic status, trying to choose a rich as possible.
This resulted in polygyny, where a few rich and powerful men would "own" most of the women. And to overcome this, the other men would have to overthrow the ruling class. This is arguably our most violent dystopian social structure.
The most prevailing method that has over come this has been monogamy, where two people would declare sexual exclusivity towards each other. This reduces hierarchies of people.
As far as MY experience, I have an uncle who got divorced once. Out of his 13 siblings who are still married. And my parents have been married for 27 years with few issues. Monogamy works when you can understand that it is a conscious choice.