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.

Exactly! Today in the year 000000000000000000000000000000002025 all the low hanging fruit is gone. Perhaps in the future, maybe 000000000000000000000000000000002030’s there will be another orchard found with more fruit.