I'm no financial expert by any means, but I do find this stuff interesting and try to follow it.
My opinion is that the Fed's QE and other strategies to get us out of the last recession were kind of a "roll of the dice". They took a chance on it because they really didn't know what else to do. In recent history, the Fed's traditional tools to control the economy (such as raising and lowering the Prime interest rate) have become ineffective. They've had to keep the rates extremely low after taking them down near 0% initially didn't really do more for them than help the poor economy "tread water". And every time they try to bump them back up again, they cause another economic stumble/falter -- which is keeping them from moving it more than very incrementally. Ultimately, the Fed got a lucky roll with those efforts and we recovered. But I'm not sure they can keep pulling us back from the brink, as we see this roller coaster of economic prosperity/recession happening again and again?
I think as our national debt keeps increasing, we're weakening the actual buying power of a dollar more and more. A number of factors have helped mask or mitigate that, such as most people keeping a good standard of living thanks to big decreases in the cost of technology. (Cheap labor from 3rd. world countries helped even "poor" people in America own big screen televisions and capable smartphones, for example.) But you can really see the weakness of the dollar in other areas, like what an education costs today, or what healthcare costs.
I think another "buffer" that helps hide the immediate problem is the fact that wealth in America tends to get handed down from one generation to the next. The current generation of people who are getting old and dying were probably the last really prosperous ones. (By and large, they got to experience the "American dream" of owning a house that was paid off in full, a car or two in the garage, a family they raised successfully, and sufficient retirement money from pension plans and other investments.) That means their kids are inheriting those homes, vehicles, and left-over wealth - so that helps smooth other the financial struggles we're in today. But I'm not seeing the working or middle class people in their 30's - 50's positioned nearly as well for their old age. What will THEY have to pass on to their kids?
That's the longer-term, bigger picture problem I see America facing. The Fed has had to resort to more and more extreme tactics (like government buying up private debts) to keep things going -- and there's going to be a reckoning for all of that.