I hope you're not suggestion that we go back to a gold standard? I wouldn't mind certain capital controls though, specifically limits on credit money issued for purchase of land.
If the US is going to remain being as prosper as the period immediately after WW2, some economic miracle would need to happen. AI and robotics could be that miracle.
The best explanation for that growth is that the burden of regulations, including zoning restrictions on building higher-density housing, and the share of GDP consumed by government spending, was much lower, for nearly every advanced economy, in the 1950s and 60s.
Look at the Japanese experience for example:
https://www.econlib.org/library/Enc1/JapanandtheMythofMITI.h...
With respect to growth in regulations that restrict expansion in housing supply, and how they have stifled economic growth in the US, I recommend this paper:
https://www.aeaweb.org/articles?id=10.1257/mac.20170388
To get an idea of just how rapidly government spending has increased in the advanced economies, see this graph:
https://ourworldindata.org/grapher/social-spending-oecd-long...
More generally, demographics cannot explain the slowdown in growth in my opinion. The age pyramid in 1980:
https://www.populationpyramid.net/united-states-of-america/1...
Seemed better suited to growth than the one in 1960:
https://www.populationpyramid.net/united-states-of-america/1...