1. The lack of marriageable women is a problem that can be solved by time. Men are prepared to marry at 40 if their work prospects are good.
2. The advent of low trust societies that doesn't rely on guanxi, but on merit can be a boon rather than a detriment. Cronyism can only go that far in a society where all are alone.
3. The absence of economic growth is a political one. In an overpopulated country, there is no such thing as sustainable growth. Whereas in the past, there are wars, disease, famine and mass slaughter to reset the population numbers, controlling fertility is the least worst option, and one that can be done voluntarily.
4. Looking after the aged is a necessity in the ages of pre-mechanization. Today, the basic needs of many can be provided by a few.