A lot of people are, in general, in denial of what reduced fertility will bring. Consequences lag effect by decades so it's not exactly a secret what the future will hold. For instance most don't realize that Japan is still in the 'good ole days', relative to what awaits them in the future, even as places like Tokyo start to shrink today.
I also think people don't realize how fast things start happening once they do start happening. For another example there you can approximate the change in population due to fertility (once a fertility rate is shared among a population) as being a scalar on population of fertility_rate/2 every 20 years. So a fertility rate of 1 means each and every woman has 1 child on average, yet nonetheless that means your population ends up declining by 50% every 20 years, exponentially, until you start having a healthy number of children again, or go extinct.
So for a bemusing one one, North Korea and South Korea are still technically at war. And North Korea is going to win, simply by continuing to exist. South Korea with their fertility rate of 0.75 will not only see catastrophic population decline, but their entire economy will collapse alongside it. Going from 0.75 to a healthy fertility rate is probably not going to happen, so the North needs to merely wait, and keep having children.