It doesn’t matter how “diversified” you are if your economy is basically broken. You can’t make money out of nothing, and real estate is as good a store of value as any other (assuming you haven’t bought an apartment made out of milk cartons and soybean waste, of course). At worst, you have a roof over your head - something the average European, at least, struggles with.
Where it matters, I would say the US and Europe are suffering from the same malaise: a belief in their own exceptionalism coupled with (oddly) a complete loss of faith in their own culture, extractive governments that have racked up debt far in excess of their ability to service it, weak governments that seem intent on sabotaging their own nations, and a general sense of despair. Fundamentally, we can’t get shit done. China, in contrast, still believes in itself, and hasn’t abdicated responsibility for its own future.
It was certainly ruinous, but I’m not sure it’s unfixable. The obvious solution would be to find useful things for older people to do - not necessarily to draft them back into the 9-to-5 workforce, but to keep them engaged in the economy in other ways - perhaps as consultants/mentors, or in social services, or as odd-job men and women. The fact that Westerners think this problem is unfixable speaks more to our collective lack of imagination and optimism than anything else - and we’d better watch what China does, and learn from it, because we’re only 20 years behind them. Birth rates are collapsing in both the US and Europe, and whereas China discarded the one-child policy about a decade ago, the West has no intention of making a correction, and doesn’t even acknowledge that it’s a problem.
Nobody’s going to shut down trade with China. China supplies the world, and that’s all there is to it. The US and Europe have largely sabotaged their own industrial base, and rebuilding it would be a long and painful process (not that anybody is even trying). China is locked into its pre-eminent position.
China is on their side, to the extent that there are any “sides”. Why people would imagine that China is going to subsume its own interests in favour of the US, though, is a bit of a mystery. Why on earth would they do that? Apart from the fact that it has been their stated, overt aim to become a world superpower and overshadow their (perceived) oppressors, they know perfectly well how the US behaves on the international stage. China has learned how to talk softly and carry a big stick. And you can hardly blame them.
There have been dozens of major wars since the end of WW2, most of them caused by the US, and almost all of them completely unnecessary. We (Westerners) have just been rather lucky they’ve been in other countries that nobody cares about.