Point 1 some people might put some blame on demographics collapse, but the core of point 1 really isn't demographics though.
It isn't, but similar forces are at play in China due to parallels in the economic strategy. Like Japan, China followed an export-led manufacturing model based around its cheap currency and a large, skilled labor force, along with massive government investment in infrastructure. And like Japan, this has contributed to a massive property bubble that is growing increasingly dangerous.
The benefit China has vis-a-vis Japan is that, as a sovereign country, it has not been possible for the US & allies to force it to appreciate its currency. Even today, the yuan trades at 0.14 to the dollar, which is merely a ~15% appreciation compared to twenty years ago.
By contrast, the Japanese yen was forced to appreciate ~90% against the dollar in just a few years after the Plaza Accords. So Japanese exports basically became twice as expensive relative to US exports, erasing its over all competitiveness and creating the modern impression that Japanese products are "nice but expensive."
Nonetheless, the property bubble, if allowed to grow, will lead to a similar credit crunch and liquidity trap as Japan suffered during the lost decade. We're already feeling it in Chinese consumers' recent reluctance to spend and invest.
Point 2 is more convincing when it comes to blaming demographics collapse, but it's more like the demographics collapse in Japan is exacerbating some more core problems.
So earlier when you wrote:
It's probably more accurate to say that the demographics collapse in Japan hasn't helped it and is likely a factor in why its economy has stagnated as it has, rather than saying it's the natural result of demographics collapse.
Here's the issue - a country with a youth bulge can get away with a lot, assuming it is competent. Credit expansion, for example, is very easy to argue for a country with TFR > 2.1, because the assumption is that a growing population = larger economy in the future, so lenders and investors are perfectly willing to extend lines of credit, betting on future growth. This is
much harder to argue for countries with < 1.5 TFR, because investors and lenders simply have a hard time believing future generations will be able to pay back what their parents borrowed.
Just the same, in terms of company culture, you can get away with a lot more with young people - long hours, quick turn arounds, rapid pivots, lots of risk taking, and of course, low pay. This is why start ups tend to favor youths - they're cheap, they're aggressive, and they're willing to bet on work that's high risk, high reward.
By contrast, older people, particularly middle aged and later, just aren't willing to do any of those. And that affects company culture, leading to the inevitable creation of "dinosaurs" that are set in their ways, filled with bureaucratic red tape, and which aren't willing to take risks. Older people want
security above all else, and that results in an economy that is more about preserving the status quo than challenging it.
This is why, even though the effects of demographics often aren't immediately obvious, I am convinced that they are, in fact, massively significant in determining the trajectory of a country and its economy. Aged countries - whether it's Europe, Japan, or South Korea in the near future - are less innovative, less entrepreneurial, less risk taking, and in general,
less competitive in emerging industries. Where they do well is relatively stable, legacy industries where experience counts for everything. This is why Japan remains strong at industries with high barriers of entry and minimal disruption, like ICE cars and high precision components.
But they're terrible at emerging industries, and as emerging industries overtake legacy industries, Japan and countries like it will inevitably decline. This is why I keep saying, "demographics is destiny."