John Hollander writes in Rhyme’s Reason: “Poetry is a matter of trope; and verse, of scheme or design. But the blueprints of verse can be used to build things made of the literal or non-poetic material –…which is why most verse is not poetry.” Certainly certain conditions must be met for verse (whether "formal" or "free") to be defined as poetry. It cannot be enough to simply put words in an array for them to be considered poetry.
If there is a set of criteria/elements (diction, syntax, line & half-meaning, trope & thought, rhetoric & speech, rhythm & combination etc...) which is necessary to define poetry as such, might there not be a similar guideline to determine whether that poetry is “good” or “bad”. Poetry (like all art) should resonate with the reader/consumer. It should as Robert Frost put it,"… begin with a lump in the throat, a home-sickness or a love-sickness. It is a reaching-out toward expression; an effort to find fulfillment. A complete poem is one where the emotion has found its thought and the thought has found the words."
Thus, it should move the reader – take them on a journey to some form of enlightenment (all the while entertaining them). If a poem does not engage us or (at its completion) has us saying- “So what?”, it has failed us. Does this make the poem “non-viable” or “bad”? Perhaps for us, as reader, but maybe not for others. If it works for more readers than it doesn’t for others; does that make it a good poem? That it is functional for at least one reader - may be a necessary condition for “viable” poetry; but not a sufficient one in my estimation for “good” poetry.
If for a moment we might imagine a circle as representing a poetic mindset, might it not be logical to assume that two circles might intersect when it comes to poetic aesthetics. Perhaps two like-minded individuals ( from the same school of poetic thought?) might be more likely to enjoy certain aspects of a poem. The overlap of these two circles might be greater than that of two readers from different aesthetics. However, by the very definition of poetry even two diverse poetic viewpoints must intersect at some point. There are certain expectations (however basic) on the part of the reader - vis a vis the pome, that must be met. Therefore, a “skillful” poem might then be one that readers from as many varied perspectives as possible can most agree upon as having some intrinsic value. Inevitably, is this not what makes a poem as viable today as somewhere down the road?