The "winnowing process" is all about limiting participation (and competition).
Dr. Menand is effectively arguing that Ph.D. candidates are not putting up a huge investement to learn more (that happens in the first 3 years) or to contribute more (a single good research paper takes about a year), but simply wasting time on a larger dissertation. (If he thought that Ph.D. students were learning lots, and making a useful contribution, then he wouldn't have written the article).
This huge investement is there to protect the cushy status of academics. To fortify the ivory tower against the contributions of dilettantes. Menand seems to think this is a good thing, but that it has been taken too far - being more selective of Ph.D. students would be more effective than making the Ph.D. a real grind.
Dr. Menand is effectively arguing that Ph.D. candidates are not putting up a huge investement to learn more (that happens in the first 3 years) or to contribute more (a single good research paper takes about a year), but simply wasting time on a larger dissertation. (If he thought that Ph.D. students were learning lots, and making a useful contribution, then he wouldn't have written the article).
This huge investement is there to protect the cushy status of academics. To fortify the ivory tower against the contributions of dilettantes. Menand seems to think this is a good thing, but that it has been taken too far - being more selective of Ph.D. students would be more effective than making the Ph.D. a real grind.