I don't like poems that seem to say, "Guess what I mean." And I don't much like symbolist poems, in which people and things are standing in for the real subjects, who for some reason are absent. I also don't care for surreal or impressionist poems that assume a reader wants to help interpret the poet's dreams.
This is not to say that I think everything in a poem should be on the surface. Not at all. It's simply to say that there should be a surface, a place for a reader to stand. Young journalists used to be taught to answer the questions who, what, where, when and why in the first compressed paragraph of a story. I would go so far as to say that the first four of these ought to be answered in a single reading of most poems.
-- Miller Williams, in Introspections: American Poets on One of Their Own Poems
I quote this not because I like it, but because I generally agree with it; with the second paragraph I exclaimed, "Yes!". (Strange confluence of attitudes...) I suppose I would say poems that keep you guessing too long. I find the first paragraph a bit reactionary for my liking. But the journalist questions, which I've never thought to apply to poetry, provide an interesting criterion to assess accessibility, even reader/writerly fulfillment. Generally, I don't feel satisfied with poems I write unless they communicate clearly on most if not all of these basic levels. But such a stricture makes me want to see what I can get away with and still feel satisfied with the effect of the poem... e.g. a poem that clearly answers the question who, but not what, where, and when, or what but not who, where, and when. Maybe such a poem would achieve a greater universality than one that clearly demarcates its where and when.