Warren Buffet 37 years later: “Buy index funds” https://www.washingtonpost.com/business/economy/warren-buffetts-hot-investment-tip-for-you/2019/03/01/534b83fe-3aaa-11e9-a06c-3ec8ed509d15_story.html

Using Warren Buffet as a data point for how smart/hard-working investors can beat the market is the same as me saying “if I work hard as Micheal Jordan, I can be in the NBA”.

If modern portfolio theory is wrong there would be piles of peer-reviewed academic research that back that up. If you could only point me in the direction of that academic research, I’ll gladly reconsider.

I’m not giving my opinion, I am summarizing the results of research from Financial Economists like Eugene Fama (Nobel prize winner).