The safety culture and degree of acceptable risk is somewhat different now, from when we were sure we'd get nuked by the Russians in a month. (And also still thought smoking was healthy.)
You are comparing a different time in the US to now. I dont think this is a fair comparison, everything takes longer now -- buildings, bridges, tunnels. I'm amazed to hear how quickly subways in NYC were built -- these days it takes a decade to build a handful of stops.
I dont think it has to do with startups vs not.
We still haven't seen any of the space startups match a manned Mercury-Redsone, which took 3 years.
During the Mercury program Nasa was using on average 0.4% of the federal budget, which was little over 2 billion a year in 2020 dollars.
The big spending was on the Apollo missions which are pipe dreams for any of the current space startups 15 years after their foundation.