Is QE quantitatively irrelevant?
Most people seem to viscerally recognize that the absence of an immediate crisis does not mean we will not eventually face one. They are wary of believing promises by those who failed to predict previous crises in housing and in highly leveraged financial institutions.
They regard with skepticism those who don't accept that we have a debt problem, or insist that inflation will remain under control. (Indeed, they know inflation is not well under control, for they know how far the purchasing power of a dollar has dropped when they go to the supermarket or service station.)
When an economist tells them that growing the nation's debt over the past 12 years from $6 trillion to $16 trillion is not a problem, and that doubling it again will still not be a problem, this simply does not compute. They know the trajectory we are on.
And when you tell the populace that we can all enjoy a free lunch of extremely low interest rates, massive Fed purchases of mounting treasury issuance, trillions of dollars of expansion in the Fed's balance sheet, and huge deficits far into the future, they are highly skeptical not because they know precisely what will happen but because they are sure that no one else--even, or perhaps especially, the policymakers—does either.