Overall quality of life is improving but if you look at the shrinking success of middle class, I believe the reason is income inequality. The economy is health when money is changing hands and more and more money is in fact locked up and not providing any economic activity. This is way the so-called economic recovery hasn't really been felt on the ground. We have a literal handful of people with more wealth the entire rest of the country. And the real sad part, is that wealth is just a number in a computer somewhere. It doesn't contribute much. Those who have that wealth can't spend enough of it to make a significant economic difference.

That inequality could be taxed and provide, for example, infrastructure which is a benefit itself but also provide jobs and generate a cascade of economic activity, like consumer spending, that simply isn't happening now.