An article about diversity in ETFs includes this figure about the prediction abilities of those who pick stocks:
A study by S&P Dow Jones Indices found that from 2006 to mid-2016, 87 percent of all actively managed U.S. equity funds underperformed the market.
In other words: not good. This is plenty of other evidence about this; see the work of Phillip Tetlock. Hence, the rise of ETFs.
One thing that this article on ETF does not address: if more business has moved to different financial instruments, what has happened to all of those stock pickers and hedge fund managers?