In general, I agree with you Ben, at least as far as people who have no time, expertise, or inclination to learn investing.

Having said that, I’ll push back a little bit and point out where the message of “invest in low-cost index funds” leaves money on the table, at least potentially.

• If 80% — 90% of actively managed funds underperform the market, that means there are 10% — 20% that outperform it. True, this is on a year-by-year basis, and not all funds that outperform their index this year will outperform it next year and the year after. However, there are funds that outperform over the long haul. My favorite example is T. Rowe Price’s Capital Appreciation fund (PRWCX) which has outperformed its index by nearly 3% per year over the past 15 years. In its 33 years, PRWCX had only 2 down years! Unfortunately for many, PRWCX is closed to new investors. However, I’m sure there are other long-term outperformers out there that are still open to new investors.
• Where individual investors have an advantage over Wall Street pros (per Warren Buffet) is that they don’t have to limit themselves to investments where putting in $10 million or even $100 million wouldn’t cause a sharp increase in share prices. This means individuals can invest in far smaller companies than most pros can. Since far fewer analysts follow micro-cap businesses, that segment is far less efficient than the Apples and Googles of the market. Thus, if you’re an expert in some industry, you might be able to identify up-and-coming star businesses and get in before the pros. You don’t even have to bat 1000 to succeed. If you can identify 10 possible winners, and end up with 5 that crater, 3 that neither make nor lose money, 1 that doubles, and 1 that ends up a 10-bagger (to borrow a Peter Lynch term), you’ll have outperformed the market by a factor of 5 or more.

Having said all that, if you don’t have the needed time, expertise, and/or inclination, low-cost index funds or ETFs are a good way to bet on the overall market, which in the long run returns ~6% — 7% a year above inflation. That means you double your investment every 10–12 years in real terms.