First, shying away from practical studies reminds me of exactly the fallacy that drove me to leave philosophy after I finished in undergrad. My experience was very similar to what pg writes about in http://paulgraham.com/philosophy.html. Asking the 'big questions' devolved into quibbling over split hairs and avoiding useful, testable hypotheses that could really make the world a better place (not that 'big questions' are bad, but we should try solving them in useful ways, not randomly)
Also, the author seems to think that a glorified form of vocational training is a bad thing. But, could it be possible to create an educational system where vocational training creates the thinking man Deresiewicz wants? That is, could an interest in say, programming, motivate studying history by examining the development of mathematics and computing machines over time? Could it lead to a study of economics through questions about the Pareto Principle or the right way to offer our programs to the public (free, product, service, and so on)? Could it lead to philosophy and psychology by asking if man is potentially programmable and why certain types of programs can't be written with our current model of computation?
In short, could vocational training take a singular interest and use it to create the sort of individuals Deresiewicz decries elite schools for failing to produce?