I have been fortunate to have paired with Joan over the last fifty-odd years in a traditional marital and family partnership. I’ve read a lot of history and anthropology and I’m not sure how truly “traditionally monogamous sexual mating” is for our species, but it has worked for us.
On observation, partnership of one kind or another does work for most people. It seems to often be two, but usually under five. It is formed by common vision _ children, a business, whatever _ and kept intact by outside pressures which are greater than internal tensions.
A true partnership is forged in honesty, loyalty, equality and mutual dependence, although the details may be invisible to an outside observer. Lots of novels have been devoted to the permutations of this theme.
In my case, I find our codependencies have aged well. We were lucky to have bonded when we were both fully mature independent people. That has kept us both relatively able to ride out problems without additional severe friction.
Anyway, I note this mostly to celebrate my good fortune. And just a cautionary note of why I distrust any demagogue with a strange singular vision of how humans should or must live.