garance

Measure, Don't Model: The Forest and the Trees

Yep. It is amazing how fast smart people forget what they have been taught in high school, Feynman saw this in teaching physics too: how students answer well one expected question, but if you ask the same thing in a different context, they fail. It is the deepest and most common educator's failure.
I think it is linked to the way that our brain stocks information in small increments and does not connect the dots unless you force it to.

Are Index Funds the Only Rational Choice?

You do not take into account that it is hard to beat a professional working at it 10 hours a day (even if recent events show that they are not always good at the job). So the benefit of an amateur research has to be very small. Plus, as we see all the time, markets have moods: all stocks came down recently, the good with the bad. Stupid as it sounds, and stupid as you demonstrate, there are still not many examples of people beating the index.