Isn't it pretty well known in the finance world that using stale public information to predict the market is a fool's errand? Unless you have some kind of specialized non-public data (e.g satellite images of number of cars parked outside parking malls, number of cargo ships moving in and out), trying to predict the market with historical data does worse than "Just give me some monkeys, darts and a dart board".
Theres actually still money to be made in small scale strategies. Sophisticated funds are running billions. They cant focus on strategies that only work for 100-500k. This is where big returns can be made. Even warren buffet will say, if he was only managing 1 million, he would get 100% a year returns.
That doesn't make sense unless there are very few viable small scale strategies, at which point they'd probably be difficult to identify. Your assertion might have been true before computers were able to help someone manage many strategies simultaneously.