I don't know if your statement about economists is intending to be a factual statement of economists' view of the state of economic science, or your opinion on what modern economic theories are good at. It's not clear to me personally, to be frank, that economics know a lot about how to create wealth either.
That said, this is not an acknowledged weakness -- Keynes' magnum opus was The General Theory of Employment, Interest and Money, which spells out in great detail how these things are related. The core of this theory is still widely held in economic circles, which is why the mandate of the Federal Reserve keeps shifting from "controlling inflation" to "maximizing employment" -- because this is thought to be something that is controllable through manipulation of interest and money.
That said, this is not an acknowledged weakness -- Keynes' magnum opus was The General Theory of Employment, Interest and Money, which spells out in great detail how these things are related. The core of this theory is still widely held in economic circles, which is why the mandate of the Federal Reserve keeps shifting from "controlling inflation" to "maximizing employment" -- because this is thought to be something that is controllable through manipulation of interest and money.