I think there's skepticism in the community that NSA et al actually have such a far head-start now. That said, historically speaking, back in the early 70s DES

I think there's skepticism in the community that NSA et al actually have such a far head-start now. That said, historically speaking, back in the early 70s DES was being designed. The NSA made some unjustified changes to its S-boxes. At the time, there were allegations that they had made them intentionally weaker. (Or so I've read; I wasn't born yet.) In the early 90s, differential cryptanalysis was discovered for the first time, and it turns out that DES was already resistant to it (unlike other block ciphers at the time): in fact, the NSA already knew about differential cryptanalysis, 20 years ahead of the general public, and intentionally strengthened DES. (Also, IBM discovered it, too, but kept it quiet at the NSA's request.)