In markets like real estate and private business, I agree with everything you wrote. In a liquid, public market like publicly-traded stocks though, I'm not so sure. I don't disagree that if you devote your life to it, you could possibly find an edge - although it will likely continue to get more difficult as institutional players become ever better at exploiting (and thus removing) any inefficiencies. But even if we accept that it's possible, you would almost certainly have to accept significant volatility to do so. And even if you didn't, you would ultimately be devoting your life to winning a zero-sum game. (Similarly it is possible to become good enough at poker or (with more difficulty) blackjack to make a living from them. Even a good living, potentially. But you're going to have to weather some downswings along the way, and you won't have any consolation in the fact that you're creating something of value - as you would starting a business for instance.)

So I guess I don't disagree with anything you wrote, but I question whether it makes sense for a person to devote the majority of their energy to playing the stock market. (And I definitely agree with you that it would indeed take the majority of one's effort over the long term to have any reasonable chance of success beyond pure luck.)

Edit: I should add that I would consider some proven, passive strategies such as tilting to small and value to be exceptions. These do theoretically allow for slightly superior returns without life-consuming effort, at the likely expense of taking on some additional dimensions of risk. I personally keep a moderate small/value tilt.