"A 1929-style crash was accompanied by mass unemployment (~25%), meaning people were often forced to sell at the bottom precisely because they had no income. You can't "hold" if you're selling assets to eat."

That's the evil thing about economic crises. People with enough capital usually can sit them out and often even benefit. People with less capital often lose everything and when the recovery comes, they have nothing that could benefit from it.

I am close to retirement and I often think how quickly your reserves can be wiped out in a long enough crisis.

Because we know of the '29 crash, the next one will always be different. Arguably the GFC was way worse, but way different.