Have I ever mentioned that it's polyamory that is the gray, bureaucratic paste of romance in the future? It's a baseline assumption for me, but I may not have described it.
We've all read James Scott at this point, or are aware of Seeing Like a State, and the ubiquitious theme that forward progress smooths out injustices and deprivations of the past, but structures a world in a way that is less impassioned, and harder to put in words or numbers, but is much more conveniently legible for others. Think about finance moving from deals on the golf courses and steak restaurants, to just spreadsheets and quants from MIT.
And this is not an unmitigated good. Almost always the modernist progress is better in many ways, in all the ways you can measure, but something IS lost. Talk about NYC 30 or 40 years ago compared to now.
Because of the current cultural groups, monogamy comes across as "the normal, boring thing to do, done by conformists" and polyamory comes across as the "young, exciting, make-poor-decisions-by-the-seat-of-your-hormones option." But what matters is actually the other way around.
Monogamous marriage is the idealistic belief that one person can be your everything, and when you meet them in your twenties you're ready to be attached to them for the rest of your life. (And earlier on, that it's only possible between one man and one woman.) These things, practically speaking, are foolish absolutes that fence our lives in.
It is much more *reasonable* that you have multiple partners, each one of which satisfies different needs, and none of you are stuck if your feelings change, and that anyone is a possible romantic option, not just one gender or culture. It's the romance that would be designed by any good city planner.
Monogamy, in comparison, sounds more like an essentially fantasy story. Cue Zizek on monogamy, and any polycule on how "sensible" their lifestyle is. Monogamy is just the thing that feels more "magical" in the good and bad connotations of the word.
Not that individuals can't make their own magic, just the "one partner, other gender, rest of your life" is the one that brings Culturally Supported Magic without you having to look for it.
Magical: you cheated on me and now I will kms
Non-magical: you slept with her but I have a boyfriend too so why should I mind.
This is the same divide as "I hunted down this animal in the forest and ripped blood from its veins with my own bare hands" vs "we plant the wheat here once a year and harvest it once a year and we don't have to move constantly." It's kings vs legislatures. And that's why royalty is such a common theme of romances - not because of class aspirations, but because royalty and monogamous marriage are running on the same metaphysics.
It's the arrow of modernism, and on paper it's obvious which one is more rational. And going forward I think that is where more of the divide will come from, rather than social conformism vs not.