This is one of Wordsworth's most explicit statements comparing man's preoccupation with his economic status and his consequent failure to perceive what is really important--nature and all it provides to the eye and spirit.
When Wordsworth notes that "we are out of tune," he means that we are no longer able to appreciate that our true goal should be to appreciate Nature. The poem's initial sentence--"The world is too much with us; late and soon,/Getting and spending, we lay waste our powers"--sets up the larger argument of the poem. Our focus on acquiring artificial goods and services to make our economic lives secure takes away what our real focus should be: the sea "that bares her bosom to the moon," "the winds that will be howling. . . . " are those natural elements that we have tuned out of being, a denial of our natural selves that should be drawn to Nature.
Clearly, Wordsworth argues that he chooses to be with "a Pagan suckled in a creed outworn," someone who, despite having been displaced by modern man, is able to appreciate the sight of "Proteus rising from the sea" (the sun coming up) or actually hear "Triton blow his wreathed horn," that is, be so close to Nature that he can imagine a mythological being as the cause of the sound of waves.
In essence, Wordsworth uses an elegiac tone to lament that modern man spends so much time "getting and spending" that he is "out of tune" with all the beauty and mystery provided by Nature.