Japan managed to get rich before it got old. It also has had 40 years to try different strategies. It is still in big trouble. You can, by the way, buy rural houses in Japan for free. It has worked itself, literally, into this demographic disaster. But by amassing per capita wealth before it got old it is doing better than China will likely achieve. The aged-dependency ratio, just for instance, is being hard felt in Japan, it will likely be crippling in China.
Korea, demographically speaking, is a dead man walking. China currently has a (horrific) TFR of 1.08. To sustain a population you need a TFR of 2.1 (not 2.0). Korea has a mind blowing TFR of 0.7. All it means is that Korea is plunging off the demographic cliff into disaster at an even steeper plunge. Just because there is an example of an even worse demographic collapse in progress should provide no comfort whatsoever.
Europe or at least Western Europe is also not looking good but once again it got rich before it got old. In addition it has been able to kick the can down the road by being a migrant destination, something that Chinese (and Japanese and Korean thus far) social norms cannot emulate.
The thing about demographics is that trends are pretty much baked in for at least a generation or so. We have a pretty good idea of how many children will be born in 20 years time because we know how many 0-30 year old there are today. There is no country on Earth that, upon dipping below the sustainable level of 2.1, has managed to up its TFR back above it. At most, some Northern European countries have managed to temporarily up their TFR from, say, the likes of 1.4 to 1.5 by spending a lot of money on pro natalist policies and programs.
China turned a fertily decline that would have happened anyway due to urbanization and industrialization into a fertility collapse with its one child policy.
It belatedly started accepting the reality of the forthcoming disaster when it raised its child limit policy from 1 to 2 and then to 3 and just this year seems to have, belatedly, fully come to its senses and removed all restrictions. Some would say it is too little, too late.
China has, demographically/statistically speaking (not literally), not only run out of children but has also run out of young adults to have those children. It boggles the mind to consider any way that China could reverse it even if it would somehow institute a Hand-Maiden level of fertility programs. However I do look forward to how China tries. Perhaps they will indeed surprise us all with an absolute miracle. A declining China will be felt hard by the entire world.
PS. For those that just don't get the problem of declining/collapsing total fertility rates, consider this:
China's fertility rate is estimated to have dropped to a record low of 1.09 in 2022, the National Business Daily said on Tuesday, a figure likely to rattle authorities as they try to boost the country's declining number of new births.
www.reuters.com
en.m.wikipedia.org