That wasn't his point. His point is that a company being successful is evidence of nothing. Plenty of companies are successful and make shit products, often on purpose. There's a whole sleuth of companies that have the entire business venture of "do what X does but shitter". And they make a lot of money.
So, if your evidence is "well MongoDB makes money" then that doesn't mean much.
Yes using JSON to store your data will kill millions of people.