Not to go off on a big gender dynamics discussion, but one of the problems facing various types of non-monogamy is that it's made out to be a joke or the source of abuse in popular culture. See Mormon Fundamentalists, any TV show about a polygynist family, etc. Also problematic is that the polyamory community, the largest sub-culture for any type of non-monogamy, generally looks down on any type of "closed" relationship between multiple people as well (ie: a group of people who do not have relationships or sex outside of the group).

A related piece of information that some people may find interesting is that the "pick up artist," "red pill," and "manosphere" groups virtually unanimously reject non-monogamy. You'd think that these groups would be all about some pro-polygyny, but very little theory for it has been developed on any meaningful level aside from managing multiple fuck-buddy type relationships.

For the consideration of people reading this, 8,000 Years Ago, 17 Women Reproduced for Every One Man, and it wasn't because the number of men and women were so different (though this did affect a small part of that).