I hope you're right, but it's typically Asian cultural strengths that are the very reasons why their demographic decline is so pronounced. The reasons highlighted for Korea's demographic decline are the desire for wealth and status, the hyper-competitive nature, and the overemphasis on a work ethic and discipline. China has many of those qualities which allowed it to propel to the top, but its also double-edged.
Just like it is already too late because of years of low birth rate for Korea, even if they can change the fertility rate to 2.1 overnight, China too has had years of the One Child Policy that are not reversible. You cannot materialize millions of 20 and 30-year-olds; the demographic deficit will manifest even if the fertility rate jumps to replacement level today. Having children is not something you can simply will into existence on a large scale; otherwise, other
Ohhh Yeah they can, but the usual suspect are going to cry fault, in fact they are already complaining. I told you what will happen when the low birth rate hysteria go out of control, someone has to carry the burden of civilization, that will be the solution. If this hysteria continues countries are going from incentives to punishment like taxing the childless and single childless adults to pay for other people children, there is going to be a lot of pressure for single women and specially young women. This what these Social Science graduates demographers don't tell to people.
China is investing a lot in automation and AI to account for future population if this hysteria takes place and they have more than anticipated children that investment has to be reduced to take into account for future jobs.
Perhaps this is simply a natural limiter placed on population, like a behavioral sink for humans.
No humans are not rats.
The biggest limiters of population growth has always been calories and health, a large population and drop in calorie intake? I don't care how high your birth rate is, your populations numbers are going down
and fast. A killer virus appear and becomes endemic killing hundred of thousands per year, that is a drag in population growth, especially if the disease kill mostly children. Africa was a big example, huge birth rates but the population growth was limited by famine and diseases. But with trade, modern agriculture and modern healthcare the continent has put more people in 2 decades that in the last 100 years before combine. If the heavens forbid
something cause a deficit in calorie intake those population numbers could go down pretty fast.
Another example. The video says South Korea is going to have a lot elderly population, that the elderly is going to surpass the young by a lot, the reality is that if the healthcare system get overwhelmed because lack of funding or too many patients,
they are going to become a young country really fast, they are likely to see the biggest drop in life expectancy in their history.
In others words what you are seeing today is something that has never happen in history,
for the first time in history most women in this planet can decide when, how, how many, where AND even with who to have children. Feminist are going to tell you that the biggest win for women was voting or entering the workforce, I would say, personally,
the biggest win for women was the invention of reproductive healthcare. Basically liberating them from early and unwanted motherhood which was the main driver of high birth rates in the past. 
