Well there's a few pieces at play.
1) deflationary population trends (baby boomers retiring and millennials taking forever to join the workforce)
2) global deflationary trends provide inflationary headwinds locally
3) QE went to banks not people
3a) We swapped from a corridor system to a floor system, which means that the reserves provide by QE now pay banks interest so it lowers the banks desire to put that money at risk by lending it out when they can get a risk free return for just sitting on it.
3b) since all the QE went to banks when it did find its way out of the banks reserves it wound up in assets as opposed to in productive economic spending. It inflated asset prices but provided no real growth.
4) The general population is overly trusting of the U.S. government and the Fed, they believe that after the Fed rescued us in 2008 that they have more power than they really do.
5) Reserve status on currency means a consistently large foreign investment surplus, which means we *have* to have an equally large trade deficit, which is an inflationary headwind.
I'm sure there are others I'm missing. Needless to say inflation is only loosely correlated to money supply. Now if the money we printed made its way into the hands of the general public as opposed to just into bank reserves and assets then I believe it would have been hugely inflationary. If we continue our flirtation with MMT we will be able to see if this hypothesis holds true. I still think Browne's agnosticism still holds though, as it was essentially the first real implementation of MPT (and to this day the most pure popularized form of MPT). The underlying fact that money always *has* to find a home somewhere, means that even if the correlations are not perfect, one of the assets will always be in a bull market. Money has to go somewhere, so something is always going to be bought. If not stocks and bonds, then real assets. There is benefit in taking highly volatile uncorrelated assets and placing them against each other in a portfolio that is regularly rebalanced.