People, I believe, intuit that the STEM fields are good majors. But I think that’s not just, or even primarily, because of their intrinsic merits. The fact that these programs are hard and the people in them tend to spend a lot of time studying is an important part of the story. By contrast, majoring in “business” sounds very practical-minded to a lot of people. After all, how could a business degree not be more valuable than some nonsense like philosophy? That’s one of the reasons why it’s become the most popular major by far. But business majors aren’t actually doing anything! Not surprisingly, in exchange for doing less work than people in other majors, business majors also learn less.
On the whole, I think Yglesias is right. It’s not a good major/bad major problem as much as a broken set of expectations. If Philosophy is a demanding degree on your campus, your Philosophy majors will be better prepared for the workplace than graduates of a substantially less rigorous professional program.