When a naturally fiery orator like Narendra Modi turns to something as dull as PowerPoint to explain himself, you know he has a problem. That’s what Mr. Modi did recently in an hourlong address to an institute for company secretaries, amid growing doubts about the Indian prime minister’s vaunted skills as an economic administrator.

Mr. Modi’s performance was characteristically confident, but also oddly bristly. He attacked critics who “take pleasure in spreading pessimism” as forcefully as he defended his government’s economic...