The snippet below is from a 2005 Slate article, and I was shocked to read what the author had to say (see the bold).

Gilbert exiled himself in more than a geographic sense: Today, he’s relatively unknown except to a few ardent devotees, such as Gordon Lish. His fourth book, Refusing Heaven, was published this March, in his 79th year, and hasn’t received much attention. His poems aren’t included in any major anthologies on my shelf. This is not only a shame, but somewhat mystifying. Gilbert isn’t just a remarkable poet. He’s a poet whose directness and lucidity ought to appeal to lots of readers—the same readers who can’t abide the inward-gazing obscurity of much contemporary poetry. Indeed, what’s powerful about Gilbert is that he is a rarity, especially in this day and age: the poet who stands outside his own time, practicing a poetics of purity in an ever-more cacophonous world—a lyrical ghost, you might say, from a literary history that never came to be.

I presume his book won the National Book Critics Circle award after this article was written. Either way, this article about Jack Gilbert is a good read.