You bring up the 50s and 60s and conveniently forget to mention top tax brackets were still sky high throughout the 70s and early 80s, and that certainly didn't help us then. The top tax bracket was 70% until 1982.
The prosperity of the 50s and 60s happened despite the high taxes and inflationary fed policy, which created a fair amount or resource misallocation, started the steady march of offshoring capital that continues today, and led to the dismal long slide until '83.
The whole "blame the rich" thing is totally misplaced bile and is populist fodder to focus the sub-100-IQ crowd on political issues. If someone makes 100x the income you do, they do not consume 100x the resources. A Maserati has the same basic amount of raw materials as a Camry. A Coach purse is essentially the same as a generic Kmart leather bag. They just tend to misallocate their resources, spending $500 for something that should be $50. Since they are never going to be meaningfully productive anyway, its actually better that way, because competing with the rich on the same playing field for resources sucks...ask anybody who lives LA or NYC.
The real problem is misallocated resouces in the broader economy. If house prices are inflating in an insane way, regular people who would otherwise be meaningfully productive, are spending their time doing $5k of repairs to a house and flipping it at a $20k profit, taking much more capital out of the market than the the value they supply. If the fed is pumping money and the stock market has nowhere to go but up, average people will invest their money in these fiat paper resources instead of investing in their own personal infrastructure, such as starting a new business or tackling a potentially profitable project.
When everyone is taking out more capital than the value they're providing (toxic capital flows), the house of cards collapses and you get a recession. Sure you can pump money into the balloon to keep it going, but it needs to come crashing down somehow. These people flipping houses need to lose their arse, and then move on to something more productive. The people "investing" in paper stock ticker need to lose their arse and invest their money into actual infrastructure that will build our economy later.
The reason we're stagnant and not growing is because the fed pumped, the government bailed out, and saved the parasites and their toxic capital flows, and they're still not moving on to building something real. We'll continue to have plunge after plunge with no meaningful recovery until we accept the necessary pain that comes at the bottom of the market cycle to clear the toxic actors out of the system.