Traditional marriage will eventually reassert as the most viable of human institutions. Absolutely every other form of “marriage” ever proposed or attempted has eventually been discarded for what it is - a fad and essentially, a dead-end, so far as its biological function is concerned.
Of course, human being are not only biological beings, and some day, the actual propagation of the young will be at least partially diverted into technologically highly specialized methods, but this shall by no means be utilized by the vast majority of humanity. The exercise of these variant forms of “marriage” exist more as a faux protest against conventional and normal human interchanges arising from immaturity, than as any practical expression of humanity.
Every civilization that has embraced these new “modern” methods of exercising interpersonal connections has eventually abandoned them, because of the very abrasive nature of most people’s personalities. The polish of civilization eventually wears even the most abrasive into a smoother and more mutually respectful aspect, like stones tumbling in a turning cylinder.
It is called “achieving maturity”. Wisdom always triumphs in the end, though sometimes it is hard-earned.
Well, nobody ever said natural selection isn’t real. Let it weed out the others.