This question totally retarded and I'm incredulous that the economist entertained it. Would the economy be better without MBAs? Really? There are people out there who are trying to tell other people that the entire economy would be much better without a small group of people spending another couple of years at university learning more about business? A better question might be 'Would a startup be better off with out MBAs?' or something more specific. But to try and claim that the entire economy would be better off because a tiny proportion of young people decided to do a masters is incomprehensible. Disclaimer: I have an MBA.
It's a serious question. Did you even read the article?
Not all that many people do law degrees, but the Economist has repeatedly covered studies that suggest the number of lawyers we have is well above the economic optimum, that having too many lawyers harms the economy.
Further, since you have an MBA, you should be fully aware that the tiny number of MBA holders have wildly disproportionate influence on the economy. As the article says at the beginning, 40% of Fortune 500 CEOs hold an MBA. So it's entirely reasonable to ask whether the degree, like a law degree, is really benefiting everybody. Perhaps it mainly benefits MBA-holders at the expense of others.
