Voice and Versification in Translating Poems

Great poets like Shelley and Goethe have made the claim that translating poems is impossible. And yet, poems are translated; not only that, but the metrical systems of English, French, Italian, German, Russian and Czech have been shaped by the translation of poems. Our poetic traditions are inspired by translations of Homer, Dante, Goethe and Baudelaire. How can we explain this paradox? 

James W. ...