I agree that it's impossible for the rates of economic growth and lifestyle improvements we saw since the late 1800s to continue indefinitely, but the key to growth is investment. And from the late-1800s till the mid-1900s, there were huge government investments made in building new and innovative infrastructure in the US--railroads, the phone network, state universities and K-12 public education, electricity generat…
According to wikipedia, more people than ever before are getting educated. https://en.wikipedia.org/wiki/File:Educational_Attainment_in... Spending on infrastructure is going up. https://www.economy.com/dismal/analysis/free/254109 The issue is not lack of investment, it's out of control costs.
"Public investment in infrastructure sits at its lowest level since records have been kept because of underfunding across all levels of government."
And the lead into the second graph, which shows real-terms per-capita public investment is:
"On a per capita basis, real government spending on structures is the lowest it has been since at least 1950."
Given statements like that, I don't see how you can make the leap from "Spending on infrastructure is going up." to "The issue is not lack of investment, it's out of control costs."