Your post presumes that a better system has been found. Gold has been tried, and the result was abject misery.
Arguing with gold bugs. Why do I bother.
I might say the exact same thing of your Keynesian perspective on economics. It too has been tried, and the consequences will be far worse.
The difference between the two is that a nation might recover from a depression, but I do not think it will be possible to recover from a debased fiat currency where our debts are equivalent to 20 times our GDP.
Fiat currency has proven to be a suicide.