It can be argued that the age of science, enlightenment, & rationalism set poetry free to enter its proper sphere of pure play. & if you accept that play is a central & "serious" human activity, there is some truth to this. But if play/poetry/childhood is framed as part of a duality in which work/seriousness/reality-principle is the more important or essential half, then poetry has been assigned to a play-pen & will be coddled, tolerated, & held in fond contempt.
I would realign these relations, with the claim that science & rationalism cannot, & will never, provide an adequate description of reality. Philosophy reaches a little closer, but its discursive abstractions are still inadequately communicative. Only the arts provide a sufficiently vivid affective-intellectual image of experience & reality. Poetry can span the distance between philosophical concepts on the one hand, and dramatic immediacy & actuality on the other. (Philosophy for its part aspires toward the condition of dialogue & drama.)
I offer these admittedly unoriginal notions to follow up on previous posts. How can poetry assume its full powers, then? I would think one critical measure in this regard would be a poetry's expressive wholeness - its willingness to patiently present & clearly "argue" - or logically defend - its sensuous, affective, or experiential subject-matter & the underlying rhetoric of same. This is what I see, for example, in the tightly-knotted & expressive sentence-structures of Keats' sonnets and odes : these poems display a striking, a startling, fusion of song & statement. Expressive logic or wholeness - as opposed to the poetry of half-statement, deflection, intimation, pose, predetermined attitude, rhetorical inflation-for-effect.
Closer to our time, Wallace Stevens reaches in this direction, with his fusion of philosophical reflection & rhetorical play. Robert Lowell simultaneously argues & suffers with contemporary history. But these are just 2 examples among many, not meant as representative figures; my purpose is to focus on a way of interpreting poetic value.