Past performance should be a predictor of future performance if the forces driving the market remain similar to the forces driving it in the past.

If they are not the same, then past performance may be a very bad predictor. But even in that case it is hard to imagine I'd do better by picking individual stocks unless I start researching companies as a full-time job.

It sounds like your problem may be forming your opinion of index funds based on the comments of people who are not financially savvy. Extrapolating an opinion about people who you admit are not financially savvy to the question of whether the financial products themselves are a good investment doesn't make too much sense to me.

on top of that, the entire argument is predicated on us stock returns over a 100-150 year time period (an unusual one at that). what's the real expected investment life of the audience? the sample is ridiculously small.