Look at almost any Stevens poem and you'll find almost the exact same voice you find in "Of Modern Poetry." Just for kicks, take a glance at "The Snow Man" or "Thirteen Ways of Looking at a Blackbird." See what we're talking about? Stevens isn't the kind of guy who'll use a lot of dissonance or harsh sounding words in his poetry. For him, the modern world is harsh enough as it is.
Another key Stevens-ism in this poem is the way Stevens will move along nicely with clear language, then drop a phrase like "metaphysician in the dark" on you. You try to move on and understand the rest of the poem. But Stevens won't let you off that easily. He ties the entire poem's meaning to the one most difficult phrase in the whole thing, and he'll make you spend the next hour thinking about that phrase.