Except for the parts where the speaker slips into tight rhyme, this poem basically sounds like really, really well written prose more than poetry. There's a rhythm to the whole thing, sure, but if you read it out loud, it sounds a lot like a beautiful sermon being spoken by a spiritual shepherd. You can hear this prosey quality of the language in a place like line 666, which reads, "If you came this way / Taking any route, starting from anywhere, / At any time or at any season, / It would always be the same: you would have to put off / Sense and notion" (666-670).
Sure, the concepts and imagery are really poetic, but sound-wise the speaker isn't going for a ton of alliteration or internal rhyme, and he tends to speak in long-ish sentences. That said, you get this opposite of this starting at line 681: "Ash on an old man's sleeve / Is all the ash the burnt roses leave. / Dust in the air suspended / Marks the place where a story ended" (681-684). Now, you're really hearing something that sounds like poetry, and the speaker moves between free and rhymed verse throughout the poem almost seamlessly. The more prosey passages sound as though the speaker is exploring spirituality, while the rhyming passages suggest that he's actually submitting to an order larger than himself (i.e., the "classical form of poetry).