I'm pretty sure monogamy is ubiquitous because it reduces social instability, not because it makes people who engage in it happier. I think the argument against monogamy on the grounds that it reduces individual happiness are pretty strong. If we can solve the problem of social instability in other ways, why not abandon monogamy if it is provably inferior?
You can argue that non-monogamy is problematic in nuclear families, but nuclear families aren't a given. In fact, the phenomenon of nuclear families might be the result of monogamy itself. Through the vast majority of human history we have formed tribes, with non-monogamy being significantly more common. Perhaps if non-monogamy became the norm, we would see a shift away from the focus on family and back towards a tribal perspective. Considering that increased rates of depression correlate pretty strongly with reductions in "family" size in the developed world, that might have added benefits.
I think people in advanced western civilizations have domesticated themselves sufficiently in general that we'd be okay with more mate competition. I think the improvement in number and quality of relationships likely to result is worth it. I also think we'd be happier if "infidelity" wasn't a thing.
You can argue that non-monogamy is problematic in nuclear families, but nuclear families aren't a given. In fact, the phenomenon of nuclear families might be the result of monogamy itself. Through the vast majority of human history we have formed tribes, with non-monogamy being significantly more common. Perhaps if non-monogamy became the norm, we would see a shift away from the focus on family and back towards a tribal perspective. Considering that increased rates of depression correlate pretty strongly with reductions in "family" size in the developed world, that might have added benefits.
I think people in advanced western civilizations have domesticated themselves sufficiently in general that we'd be okay with more mate competition. I think the improvement in number and quality of relationships likely to result is worth it. I also think we'd be happier if "infidelity" wasn't a thing.