For thousands of years, the preservation of civilization has rested upon most men and women having no choice but to marry the best person available to them, and have enough children to support them in their old age.
Since WW2, it has become possible, and increasingly acceptable, for people to remain single and childless. It remains to be seen whether civilization will be able to survive this.
This has been the trajectory since the Industrial Revolution and a mass exodus from agriculture.
I agree it is an experiment, but not one that can be pinned on the “leftover women” of China.
The “leftover women” campaign is as old as the hills. Blame women for all of societies ills. That’s even older than marriage.