Your problem is with consumerism.

Entertain for a minute the though of a world with absolutely no consumerism or financial elites where no-one ever buys anything unnecessary or made of plastic.

In a deflationary scenario, everybody holds on to every dollar they make which they don't have to spend on nevessities. Savings account are worse than the underside of the mattress, since deflation means negative interest rates by definition.
So where do you find the money to finance medical research, new roads, or anything that would return a future net benefit to society? Money under a mattress serves no purpose to society whatsoever.