I couldn't disagree more strongly on "Isle of the Dead"--at least with such an offhand dismissal. It is a hypnotic, evocative, otherworldly work that does what it intends to do admirably. It's one of those rare pieces that is both approachable and stands up to repeated listening. It takes you into another world, but one which is not Chabrier's "Espana."
Now for Ashkenazy, he's often at his best with works that require both technical excellence and a finely honed balance between bringing out both the beauty and the darkness that, as part of the human condition, makes that beauty all the more affecting. Listen to his piano recording of Ravel's "Gaspard de la Nuit" especially, "Le Gibet." For a good contrast in his conducting style, trying comparing his set of Sibelius Symphonies with the very fine, much brighter set, conducted by Colin Davis. Ashkenazy has long been one of our most reliable, thoughtful, interpreters of great music.
And brilliant Rachmaninov: Stravinsky's, "six feet two inches of Russian gloom," do we dismiss him because he can put the "Dies Irae" theme into even "Variations on a Theme by Paganini"? though sometimes sprightly or martial, we find him more often achingly beautiful framed with a poetic melancholy.
A cure for euphoria? Euphoria has its place, and its repertoire--but so does dreaming.