It’s true that “average returns” are not particularly interesting to look at, and do not take into account the effects of compounding.

That’s also both irrelevant and highly misleading, since when people actually talk about stock market returns, they are using average annual growth rate (also known as compound annual growth rate), not average returns. That’s what the 10% number commonly discussed is.

And that number is also the stock market as a whole weighted by market cap, not the DJIA which is 30 companies weighted by stock price.