i think you’re taking that quote out of context a bit. a few sentences later, the article says

Even physicians have weighed in on the shortcomings of B.M.I. The American Medical Association warned last year that B.M.I. is an imperfect metric that doesn’t account for racial, ethnic, age, sex and gender diversity. It can’t differentiate between individuals who carry a lot of muscle and those with fat in all the wrong places.

“Based on B.M.I., Arnold Schwarzenegger when he was a bodybuilder would have been categorized as obese and needing to lose weight,” said Dr. Wajahat Mehal, director of the Metabolic Health and Weight Loss Program at Yale University.

so the point they seem to be making is that, while BMI is controversial partly because people like to shoot the messenger, it’s also just not a reliable measurement in a medical context, even as a heuristic. the article also goes into more detail on its other shortcomings as well. the article also indicates how BMI was never intended to be used in a medical context. so, there are plenty of valid reasons for wanting a new metric.

but i do think the sentence you quoted isn’t really doing the author any favors in terms of trying to communicate the central point of the article.