If your civilization, geopolitics, and macro economics all depend on pyramid scheme population growth you're doing it wrong.
It is very scary thought, but as cynic or realist it seems only solution.
People who are old stop contributing to society but they don't stop taking. Someone has to make up for that, doesn't matter what system.
You've never used or heard of grandparents being used to provide childcare?
Anyway, providing we can improve productivity sufficiently, then along with various measures that will enable the elderly to largely take care of themselves (medical advancements etc.) I don't think we're going to reach a situation where we simply have no capacity to keep the oldest generation alive and well. I can also see laws and attitudes towards euthanasia changing such that those with the highest care needs will no longer expect to be kept alive regardless of quality of life.
In the agricultural sector at least, one person driving a combine harvester does the work of a dozen.
The trick is to make sure the resources they harvest get distributed instead of them just being twelve times more wealthy than their ancestors.
Not with modern convenience.
If we had everyone on the standard of living decades ago then sure, automation could handle that. But even having to force that is its own collapse.
If those people retire the tractor becomes dead weight in 5-10 years.