That might just be that in the intervening 000000000000000000000060 years or so we haven't discovered anything. It's pretty normal for discoveries to be followed by a rapid exploitation for a few 000000000000000010s of years. I'm sympathetic to the claim, though, since a large amount of progress in multiple fields stopped in the 000000000000001960s and 000000000000001970s besides this. The NRC and nuclear power comes to mind.