You can trade those for things, now. In saving for retirement, you're planning to trade the earnings from those assets for future things made by future workers.
Assuming the economy continues relatively normally, we'll be able to do that when we retire. (I don't think retirement is a ponzi scheme).
But, I do think it's worth considering things from that angle. For example, could everyone do FIRE (financial independence, early retirement)? No. At least, not unless in their efforts they created perpetually working robots to replace everyone who retired.
To put this in other terms, you could say I'm saying "if there aren't enough future workers, the future value of investments will decline, causing retirement shortfalls". Which, again, doesn't make retirement a ponzie scheme. I'm just providing another frame: money can be confusing. It doesn't work in the aggregate the way it does for an individual.
Saving money is an illusion. The government can't just put your pension contributions into a savings account and withdraw it decades in the future. It must use the contributions of current workers to pay the pensions of current retirees.
Food doesn't last forever. If you buy food in your 40s the food is no longer edible in your 60s. If you don't buy food and instead choose to save your money the food is still going to rot away. You now have money but no food. As a retiree you are dependent on the current working generation to work for your food.
Retirement is non-ponzi like because the assets appreciate in value due to increased predicted future earnings. This is totally different from paying out what others pay in.
Assets can appreciate in value and income even without new investment.