I'm afraid I have to disagree with some of your conclusions.
They were born into one of the most, if not the most, prosperous times in the history of humanity. The foundation of this prosperity was planted by their hard-working ancestors, and they grew up in it and eventually inherited it, so they can't actually take any credit for it.
They were lucky. Their immediate ancestors were the group of people who caused the Great Depression, still considered to be the worst economic collapse this country has ever experienced. The government was largely unsuccessful at fixing it until World War II rolled around and restarted our economy. Suddenly the manufacturing capacity was needed to supply ourselves and our allies with weapons.
In hindsight, this was the peak of middle-class America.
I'll agree with that, but point to WWII as the source again. Must of the rest of the industrialised world had been destroyed by war. Factories and production through out Europe and Japan had been destroyed to win the war. The US responded by rebuilding them, which involved selling our industrialised services to them. When you are the biggest or only source of an item or service, of course you will be doing well.
One such concept that they embraced was outsourcing/offshoring.
This to me is just the conclusion of the rebuild efforts. The US being the only source of high tech products was not a sustainable model. Other countries were sure to develop similar abilities. An example, you never hear much about non-American cars from the 50s. But with the 60s you start to hear more about European cars (like the VW bus so popular with the hippies you metioned) and with the 70s you start to see the sales of some of the now iconic Japanese cars (like the Honda Accord). Similarly during the 50s airliners were generally a US product from companies like Boeing, Lockheed, and Douglas. Once the 70s rolls around and you see the start of Airbus.
The Boomer's precious offshoring, outsourcing and "free trade" destroyed the American manufacturing sector in the 1980s and 1990s.
No, our economy would have declined even had none of those practices ever been employed. We had it good selling to the entire world after a major war. The rest of the world caught up, wanted their share of the pie, and were willing to do things cheaper than we were. We would have lost sales to the rest of the world either way.
So in conclusion, the Boomer's ancestors f-ed things up every bit as badly as we did (the Great Depression), WWII saved our economy and we were lucky there were no major strikes on the US mainland, and finally the world recovered and our position as the dominant producer became unsustainable.