I used to think this, then I worked on a trading system in an investment bank. Don't underestimate how quickly and easily you can learn and exceed people who should know what they're doing, given sufficient motivation.
The fact that you saw some people you perceived to be clowns once, does not demonstrate the market is anyone's for the taking.
What Buffet does and what HFT do are completely different. The reason why Buffet has to change how he trades is because of HFT. If Buffet puts in an order for 100,000 shares of Coke (KO) while it's at $40 a share, he would not stand a chance. HFT bots would swarm in and scoop every last share of KO that's available and then sell it back for incrementally more. All within a fraction of fraction of a fraction of a second.
I agree there must be some niches are that are amenable to exploitation by small independent traders (perhaps anything to do with nanocap stocks).
I have not had success finding niches where I thought I would be successful, but I could very well be insufficiently clever.
But trading highly liquid equities on a multi-day timescale (the strategy proposed here) is certainly not prohibitively hostile territory for large, sophisticated buy side operations.