Then I realized: the internet; the power-grid (at least in most developed countries); there are things that don't actually fail catastrophically, even though they are extremely complex, and not always built by efficient organizations. Whats the retort to this argument?
I think you could argue AWS is more complex than the electrical grid, but even if it's not, the grid has had several decades to iron out kinks and AWS hasn't. AWS also adds a ton of completely new services each year in addition to adding more capacity. E.g. I bet these DNS Enactors have become more numerous and their plans became much larger than when they were first developed, which has greatly increased the odds of experiencing this issue.
This has gotten significantly better in recent years, but it used to be possible and common for a single misbehaving AS to cause global issues.
Texas nearly ran into this during their blackout a few years ago -- their grid got within a few minutes of complete failure that would have required a black start which IIRC has never been done.
Grady has a good explanation and the writeup is interesting reading too.