Not even capitalism. Every economic system has pensions and healthcare costs rising with age, coupled with a decreased productivity.

You decreased productivity of the elder, as a society we are getting more and more productive. We create more and more billionaires.

Productivity isn’t our problem, distribution is.

I see these as separate issues.

On a macro scale you want to see country wide economic statistic numbers go up, regardless of who the money gets to in the end. When your population's age isn't evenly distributed it causes spikes in productivity and costs associated with the elderly which makes the metrics go down. Combined with short term politics that are not incentivized to prepare for it, but rather to play hot potato with it, it makes for interesting situations. If, in the worst case, the country is functioning paycheck to paycheck, you have every member of the workforce supporting multiple elderly and children via taxes, since their taxes were already spent on X or stolen long ago during the productivity boom.

Capitalism needs private property and free markets. Everything beyond that is cultural

Capitalism does not need and has never had free markets, though some arguments for capitalism being ideal rest on the assumption of free markets, along with a stack of other idealized assumptions, like human behavior conforming to rational choice theory.

Then explain why capitalism made China its workbench.

China encourages exports and has no recent history of confiscating property owned by foreigners. Combined with cheap labor this makes it a great place to set up sweat shops. If you are selling a good that can be made in a low labor area but you use high cost labor you will be outcompeted and the market wont buy your expensive products so over time all the successful firms make their low skill products in sweatshop zones