Dear John,
Your critic gets the meta-point right: art, like many other things, chiefly time, cannot stand still.
But in writing about art the specific points are more important than the meta-points, because we read poems, not Poetry, and look at paintings, not Painting. So someone who said, “The appearence of Gothic architecture was a necessary effect of the maturity of the northern races at the beginning of the Middle Ages, but the Cathedral of Chartres is as ugly as a railroad shed,” is a bad architecture critic. Someone who said, “By 1760, Baroque music having run to the end of its thread, it was inevitable that composers would turn to lighter textures and more dramatic forms of construction, but everything that Haydn and Mozart composed is witless cacophony,” has a tin ear. And someone who says, “Poets couldn’t keep rewriting late Romantic and Georgian verse, but the poetry that Yeats and Eliot wrote is as squalid as Lenin’s Russia, though not as wicked,” has simply dropped the ball. It doesn’t matter what else such a person has written or thought; he may be a great man; he may be a great poet. But he has misunderstood a great era in the poetry of the English language.
Glenn Gould said Mozart died too late. That was wrong, even though Glenn Gould’s performance of the Goldberg Variations is terrific.