Polyamory is like communism. The idea sounds appealing in theory, but society has yet to come up with a successful example.

When I lived in the bay area, open relationships were quite popular. Unfortunately, this inevitably led to way more problems than it was worth. People would often pretend to be okay with polyamory, but deep down they would grow more and more jealous and resentful. I rarely saw an open relationship that lasted and the ones that did were always fraught with tears and drama.

Animals are evolutionary hardwired with a desire to pass on their genes. Humans are better at hiding this than other animals, but it's still true. This leads to the paradox that humans want to fuck as many partners as possible, but they also want those partners to be exclusive to maximise the success of their offspring. And even if we could overcome this evolutionary desire, the fact remains that sex is a scarce resource, and that inevitably leads to conflict and jealousy. Any time your partner spends having sex with other people is time not spent with you. People are selfish, jealous creatures, and that's not going to change any time soon.