The economy hasn't really been seeing slow growth. It's slow in the sense that we had a huge downturn and we want really exceptionally strong growth to get the labor markets strong again, and we haven't gotten that (also, for people who look at nominal growth, it looks slower because inflation has been so low). But it's been pretty good, and it's been positive for a long time so we are slowly getting back to normal.
The labor share of income has been declining since the 1960s (though it reversed sharply from 1997-2001, before correcting). I don't really see how QE is supposed to have contributed to that. It helps stock prices in a variety of ways, but it also helps the labor market.
I don't know that deflation by default equals no growth, but it's certainly a drag on growth (increases debt burdens, which reduces demand, and discourages spending and investment, and it also can lead to higher unemployment--think of the argument against MWs and apply that across all wages). Low inflation also does all of that, but not as much.
And I'd agree that central banks have their priorities all wrong, but in the exact opposite way. It seems to me that they have been excessively afraid of inflation and not concerned enough with boosting employment. Though, really, the effectiveness (for good or bad) of central banks is way overstated these days. In normal times, it's the opposite. For all the talk about it, fiscal policy (tax cuts/increases, spending) doesn't really affect the economy because central banks are running the show. That is, the Fed can effectively counteract any effects of fiscal policy. But with interest rates as low as they are, the Fed can't effectively counteract contractionary fiscal policy and wouldn't want to counteract expansionary fiscal policy. As is often the case, the big fights are over distributional issues. The right is freaking out because they fear the inequality-reducing effects of higher inflation, though they're presenting the case as being the opposite (see earlier in this thread how Ultra--a far-left guy--cited an op-ed from a Republican hedge-fund billionaire expressing concern that low interest rates could *increase* inequality--LOL).