I agree with you in theory. However, over the course of 100yrs you also need to worry about entire countries disappearing. If your index fund is denominated in the wrong currency, held by the wrong custodian, or has too many companies based in falling countries, you might be in trouble. Meanwhile, Gold has survived a thousand generations.

In a hundred years, there can be wars, reparations, and lots of damage to equity.

I think some distinction should be made on store of value (win for gold) vs asset appreciation (win for stocks), especially once you start talking about 100years.

When your country collapses, you tend to find practical matters that make gold a poor store of value, unless you dissolve your gold bars in acid when the war starts.

My impression is gold is largely seen as a low risk inflation hedge rather than a growth investment. A better comparison would be a savings account or maybe municipal bonds.

Did index funds exist 100 years ago? I'm pretty sure passive investing is a more recent phenomenon.

>In 1926, it developed a 90-stock index, computed daily.

https://en.wikipedia.org/wiki/S%26P_500#History

This is just a technicality however. In practice you have to buy stocks according to the index yourself or invest into a fund that mirrors the index for you. The secret sauce in ETFs is that algorithms do the work of the fund manager and thus reduce costs.