$[$Related to Solved Problem $6\mathrm{.}3]$ An article in the Wall Street Journal noted that in $2019,$ for the first time, the total value of stocks held by index funds was greater than the total value of stocks held by actively managed funds. The $-$ article observed, "The challenge to traditional stock pickers began more than four decades ago with Vanguard founder Jack Bogle's introduction of the first index mutual fund for ordinary investors in $1976."$

What does the article mean by "traditional stock pickers"?

The article is referring to