And that's the crux of the issue: Individuals in most western societies are currently better off not having children, while society as a whole absolutely needs individuals to have a certain amount of children or run into serious issues down the line.
Many societies (for example South Korea) are feeling this more and more. Way too many old people and not enough young to run the country and take care of the old. In those places not enough is being done supporting those who chose to have children for everyone's sake.
Foregoing children and having saved for retirement does not mean much if in 40 years you're competing for the now extremely limited basic services against people who are in the same boat. Worse, young people may now decide that they don't feel like feeding and providing for a large population of old people through sky-high taxes and being the victim of rent-seeking. They just might throw in the towel and leave for a more functional country, using their now higher income to support their own parents, but none of the others. Who now takes care of the childless?
It's going to be human misery on a scale you would expect to see in a modern society.