No, Keynesian economics is not how America recovered from the depression, nor was mobilization for wartime production (checkout the book "Keep From All Thoughtful Men" for a truly in depth analysis of the US economy during that period). No, abundance and worker productivity are not why unemployment is so high and the world economy is on shaky ground. None of these things are correct, and buying into these theories leads to erroneous decision making that will serve to exacerbate the problems rather than make them better.
Much of the problems describe are due to government action, not economic transformation. The labor laws that exist today are tightly coupled to a particular model of employment and work which is no longer dominant in the economy today, and the impedance mismatch causes a huge reduction in economic efficiency as well as misery and limitation of opportunity for many workers. Onerous regulation, as exists today in every aspect of economic activity, heavily favors the consolidation of economic activity into large corporations. And that disadvantages the individual worker in a variety of ways, as well as limiting the innovation and responsiveness of the market, down to the scale of the lone entrepreneur.
Add to that the deterioration of public education in America over the last quarter century (to such a degree where even basic literacy cannot be presumed of the holder of a high school diploma) forcing the escalation of credentialism for many entry level knowledge worker jobs toward college degrees. Meanwhile, the widespread availability of cheap, government backed student loans combined with the disruption of public funding for many public higher education institutions has led to a massive explosion in the cost of higher education. At the same time "trade school" education has become denigrated in society even though many of those jobs are high paying, well in demand, and the necessary education is often quite affordable.
Add to that the bursting of a real estate bubble of unprecedented size in the US and the follow-on worldwide financial crises. Much of it caused or exacerbated by the same reasons as above, regulation and government backing creating banking institutions that were "too big to fail", but not too big to gamble to the tune of trillions of dollars. The worldwide economy still has yet to fully recover from that disaster.
Add to that the profligate borrowing of the world's governments as if there was no tomorrow. Except tomorrow has come, and governments that have been collecting as much revenue as they possibly can and using it on social programs that everybody likes are finding that they've created a system with insufficient slack to deal with any disruption, even disruptions such as paying the debt they owe before it blows up in their faces.
It's facile to blame the economic problems of today on technology. It makes it seem as though these problems are some sort of inevitable consequence of advancement when in reality they are the product of specific choices that are now coming home to roost.