The whole idea of passive investment is no management and no timing. That's proven to outperform most active management. Yes, you could get unlucky, the world can collapse into chaos, humanity could get destroyed, or various other risks. Definitely owning the US stock market over the last 70 years would have had a pretty good return.

So we just need another world war with the associated period of rebuilding and massive economic growth due to the development of integrated circuits and women joining the workforce.

You don't think the developing world continuing to develop will have a version of that effect?

Maybe. Maybe climate change wrecks the economy. Who knows? Past performance is not a great indicator of future performance.