Efficient market hypothesis is nonsense. A lot of institutional investors are long-only. That is their mandate. All the information they may have does not change that fact.
It is unlikely that you will beat the market in the long run and if you do, it may well be down to chance, but it is possible, because the market is not perfect.
Furthermore, you can not "buy the market" in the first place. You can buy ETFs replicating stock indices, but that is not the same. If you bought the S&P you will have performed differently than if you had bought MSCI world. Ultimately, stock picking is just a less diversified version of buying an index.