I only know Auden through his better known, frequently anthologized poems. Would it be true to say 'vision' was a preoccupation? The Shield of Achilles and 'As I walked out one evening' involve visions, and 'Lay your sleeping head, my love' explicitly uses the word -- "Beauty, midnight, vision dies". (Or "fades", I think, in some versions).
Incidentally, I just noticed that in The Selected Poems the piece is titled "But I Can't".
Anyway, I think this is my favourite villanelle. One quality of a good villanelle is that on reading the two repetends in the first stanza, you spend the rest of the poem aching to hear the two come together as the closing couplet, and the intervening stanzas are a tease.