Before, society grew with the average working age person only needing to half support an elderly retiree. Now, that same working age person will need to support more than 2 elderly retirees themselves, over 4 times the resources.
Has it occurred to people that, maybe, modern fertility is a tragedy of the commons? If everyone chooses to act in their own interest, society is worse off than collectively pressuring to have more kids? Ideally, that would look like major subsidies and benefits to parents to account for the extra work they are doing for society.
I fear if nothing else changes, developed countries are dysgenically wiping themselves off the planet, and the traditionally oppressive-to-women societies will evolutionarily outlast us.
At this rate, there will only be 3m South Koreans in 3 generations. I don't see how you expect a country to survive that decline. In 1960, Pakistan had 45m people compared to South Korea's 25m. Now, Pakistan is forecasted to reach 450m in our lifetime as South Korea implodes. That looks like our future.