Cash flow is a derivative of money cost and money inflows
Cash flow is a metric that relates to sustainability in a world where money is the medium of exchange. Cash is used to pay bills.
Money inflows may come from revenues which are a function of price, or they come from financing or some change in the balance sheet like sale of assets.
Economic activities that result in a persistent cash deficit will fail in due course, simply because the money runs out.
The timing of the demise of the activities may be delayed by borrowing ... but that also will fail in due course.