OK, I made an error above. Thanks for catching it. Yes, I have somewhat overstated the benefits of saving in a 401k. In my defense, it's been two years since I last fiddled with my settings, so I had lost track of what was what. Still, let me explain my mistake.
1. My employer matches 50% of my contribution up to the cap. Not entirely uncommon at big tech cos, but maybe less common in smaller enterprises.
2. I also did $50k of in-plan conversions over the last two years.
After you take all those sources out (and the resulting investment proceeds from the funds from those sources), my total is only $400k. I do still think it is correct that someone investing ($2019)5k/y since the 80s would have generated a sizable nest egg by now, but my own experience does not make that case as strongly as I had thought.
Actually, when I run it through a calculator assuming 5% total returns, it looks like that hypothetical person only saves about $700k. Which is enough to live a reasonably good life in retirement, but not marvelous wealth by any stretch.