Im gonna take the counter argument (lol play devils advocate) and say what's not to say Warren Buffet had good dose luck. (George Soros is a better example based on the amount of trades but once again a outlier ) , not lot of people actually beat average market returns few do with that said some people confuse skill with luck.
my personal hypothesis regarding the market is that it shifts from efficiency to inefficiency but is largely efficient 80% of time with 20% being inefficient (i would love to analyse world class traders trade record and see his distribution of returns probably mostly break even with 20% where large amount of money is made ? Mav your thoughts...) with that being said behaviour economics is pretty cool to study ( influenced by prospect theory lol an mav) which helps shed some light why price might move from efficiency to inefficiency, i guess it come down to how people perceive the end outcome relative risk which one can argue is driven by emotion.
I agree the market is mostly efficient most of the time ie. the price of KO or MCD is probably fairly priced right now. Whether central bankers attempting to control investor behavior is a hallmark of complete market efficiency is a question. Of course there are bubbles and panics. Of course all investors and traders aren't rational or acting rationally all the time.
I leave with this quote from the book Maverick Trading (isn't this Mav74?):
"EMT fails to adequately take into account fear and greed among market drivers (institutional investors)." Pg. 4