...and then the punchline is that you should be doing that in a mono relationship, too.
So many conflicting calendars, and scheduling issues to deal with. Especially if some/all of you have children..
Many couples see the death of one partner, many couples lack a full and complete skill set to teach children all that they might want or need to to know, etc.
Leaving communities and extended families out of the picture is some post WWII idealised nuclear family fantasy.
But are all those other people on the same 'level' of attachment for the child, or is there a 'hierarchy'?
Further, not that having community is bad, but it can 'devolve' into tribal/clan thinking, which is probably not good for society as a whole (can lead to nepotism, which is generally highly correlated with corruption) and something the West is relatively unique in 'breaking out' of:
* https://www.theatlantic.com/magazine/archive/2020/10/joseph-...
That just adds to the chances of instability between parents. 2 parents is essentially a stable maximum