it would seem that the quote you cite speaks against the essay being pro marginalist anyway the essay is not based on the premise that marginalism is correct rather it just takes it seriously rather then dismissing it out of hand and the new school is pretty unorthodox with a mixture of marxian and post keynsian economists while it does think folks like jevons and walras insightful i don't think it considers folks like ricardo or marx ignorant at all and if you read down to paretian revival some of the issues in the quote are addressed however we can put something like the quote in the criticism section that utility is unobservable that utility is not measurable this is actually realistic in my opinion the difference between cardinal and ordinal utility that utility is generally untestable though predictions derived from marginal theory certainly are and i really don't understand all this stuff about air and water the marginal utility of a bit of air is essentially zero hence its price is essentially zero and i happen to both desire and pay for water