Most people don't just think the world should be run meritocratically, they think it is meritocratic.
Meritocracy doesn't work when some people benefit from the system disproportionately.
Complex problems undermine the very principle of meritocracy: the idea that the ‘best person’ should be hired. There is no best person.
Look at Wall Street in 2008, and the White House right now. Diversity—of people and cognitive perspectives—is crucial for avoiding failure.