The year is 2034. America’s “magnificent seven” firms make up almost the entirety of the country’s stockmarket. For Jensen Huang, the boss of Nvidia, another knockout quarterly profit means another dizzy proclamation of a “tipping point” in artificial intelligence. Nobody is listening. The long march of passive investing has put the last stockpickers and stock-watchers out of a job. Index mutual and exchange-traded funds (ETFs)—which buy a bunch of stocks rather than guessing which ones will perform best—dominate markets completely. Capitalism’s big questions are hashed out in private between a few tech bosses and asset managers.