We should hope that older works stay in jobs as long as they're able. The coming demographic bulge isn't pretty.
Imagine an island society, with a bunch of 40 year old workers. You own the company that gets all the profit from their labour. So, you have a real resource, which you could trade with other places.
Now of course this island has no children. How do you feel about your investment once the workers reach age 80. It wouldn't produce very much. In fact you'd need to put resources in just to keep your island ex-employees alive.
But that's an extreme example. Let's suppose that 20% of the population is only 20 instead of 40. When the current 40 year olds hit 65 and retire, the younger generation will be 35 and can support them. What happens to your profits?
They will probably still either collapse or near collapse. You had 100% of people in the labour force, now you have 20%. This poor 20% not only has to support themselves, they must support the 80% idle old. And that's before any surplus is generated for your profit as owner.
So, your savings in the form of ownership of the island weren't very useful. It just dies out.
Could you saved otherwise? Not really. To a limited extent you could store the outputs of the island. We do this currently with grain reserves, oil stockpiles, etc.
But most of the stuff we consume are produced in the same year. You can't save real goods, only ownership of entities.
So if the entities all have a shrinking labour force, they aren't worth as much. The old people in the us won't have meaningful assets with which to pay for their care.
(The one exception is a small old country that owns rights to part of the output of other countries which are younger. There's also an exception for automation, if the companies owned by the old are massively more productive per worker by the time the demographic bulge retires)
You're making the mistake of those who think that money itself as wealth, as opposed to a medium to exchange for wealth. Money is mostly fungible, but in edge cases it just can't buy certain things.
Such a society would nonetheless face much difficult if the worker/retiree ratio changed from 100:0 to 20:80. That's true regardless of individual productivity level: case two is harder than case 1. Regardless of capital stock such as ports, rail lines, buildings, etc
And here is where it gets funny. I wonder how pension systems would look like if they were supported by the billions of dollars that especially FAANG but also other huge megacorps such as IKEA, McDonald's, Burger King "creatively avoid" in taxes. Or if minimum wages were set so high that a pension built on a life of minimum wage were enough to live on in old age (this is a problem that currently runs high in Germany, as many old people have not enough pension to get by and so require social welfare)?
It's not like the people running these corporations are all evil and out to ruin people's lives. People behave based on the incentives laid out in front of them and the current combination of capitalism and laws incentivizes the behavior we are seeing.
True, but the same people also largely support programs and politicians that preserve or extend those incentives. They're not innocent bystanders.
And corporate taxes are just taxes on people, in the end (the owners of the shares). If there are fewer people working and more people to support, things just get harder, absent large productivity increases or immigration of young workers.
Pension systems own the FAANG companies. For example, in the US, CalPERS manages a third of a trillion dollars. Two thirds of that is in equities such as Apple.