And yet ultimately that’s what every retirement and disability system of any kind has to be based on.

There's a fundamental distinction to be made to the below point of yours:

If you want to live in a world where you yourself will not be cast out onto the street to die when you are too old to work, then for some of your later years you will depend on the labor of others, just as you did when you were a child.

I strongly disagree with your first point, but maybe you misunderstood me. Investment returns are basically letting other people work for your profits, with nothing given in return. I.e. a form of wage theft (or other shenanigans like messing up the environment for profits or exploiting resources or funding a totalitarian regime).

Your second point - while correct - has nothing to do with my criticism of (stock / fund) investment returns: That could be (and was for a few decades, at least in Germany) a generational contract, where society manages to pay out pensions from which elderly / retired people can afford living & care from the GDP. Those pay-outs have been paid in advance by those needing them because they funded the old and retired people at the time they were still in work.

For that system, you do not need any kind of finance products. Of course that doesn't keep our corrupt governments from spending our retirement money elsewhere and investing in shady funds for private profits and shitty retirement payments. So in today's world, in practice, yes, people rely on finance product returns for their retirement savings and most of us have no choice in that. But it wasn't always like that, and it should not be, because it's a pyramid scheme.