The Augustans are turning in their graves.
Perhaps this is where a clarification might be necessary: I can see where one might find meaning in and object or ideal, in an abstract fashion, and be inspired by this meaning to portray said object or ideal. However, as you said, "the deliberate search for meaning... rather misses the point".
I would further state that, as "the mysteries of being human" are not the same as "mysteries of a human nature": the former, I would assume, would include our wondering at our intelligence, our ability to reason, to feel emotion, &c. My meaning, by the latter, was "mundane nature of thoughts of/created by humans, when compared to the emotions and senses invoked by an object ćsthetically pleasing enough to be worthy of artistic expression", which implies that the ordered thoughts of humans are secondary to the primary emotional responses of humans, among other things. They are "mysteries created by human nature", I suppose, and not good ones. Superfluous ones. Effectively, n order to condense what could have been an entirely long and boring description, I went vaguely and tangentially philosophese on yo' ass.
Re: Metal. This is where the second half of that quote of myself is required. While, most certainly, there is definably good and definably bad metal in the world, I am all for allowing people to listen to what they want to (as long as they don't insist on pushing it upon me). If somebody listens to Slipknot and thoroughly enjoys it, then, to that person, "in [his] own opinion", to quote myself, it is good, and Slipknot are "directly communicating with [him] through [their] [utterly shit] ["music"]". Also, why remove "metal" from "art"? I would suggest that Metal - good Metal, mark - is Art.
Perhaps our definitions of "art" are different. I would define "art" as being "the human attempt at expressing any object, emotion, ideal, or concept, through physical means". Wikipedia, the worst encyclopedia in existence (but all I can be bothered to use for now), states: "Art is the process or product of deliberately arranging elements in a way that appeals to the sense or emotions".
Amusingly, upon looking at the Wikipedia article on "Art", I've realised that, somehow, my concept of what art is, is, effectively, either artistic "Realism" or artistic "Objectivism".
My final point is an outright rejection of your statement that "art for the sake of art" does not exist. There are many "works of art" (again, definition required. Bloody philosophy) by many people who would happily say "Oh, I just like to make music/paint/draw/whatever". This could be for personal enjoyment, for the sake of it, for both. It is, I will accept, an ambiguous statement in that regard. Still, there is no prerequisite of art that it must represent something other than what it obviously represents. I would say that most art can cause emotions and thoughts in the viewer other than those experienced by the artist, but that fundamental object/ideal is the central point, the focus, the anchor of all conjecture conjured by the work. All good poetry, should it choose to meander through thought, will return to its original point.
Shelley's "Alastor" (Shelley was not an advocate of Negative Capability, though he admired Keats greatly) had, according to him, a definite "meaning", as it were, which is that a man should not be a recluse, should not shut the rest of the world off from him, and he from it, for it inevitably leads to a death similar to that in the cold, barren wastes, as experienced by "the Poet". Many have argued that this goes against Negative Capability entirely, as it is "reaching after fact and reason". I would dispute that the primary ideal that Shelley had in mind when he wrote "Alastor" was that men should not distance themselves from others to the point of abject and complete solitude. This is the sentiment conveyed by the poem. Shelley stated no other reason for writing the poem (other than, of course, to write a poem). It conforms, thus, with the concept of Negative Capability, and is a primary example of a poem, the fundamental ideal of which, is not explored, nor extrapolated on, and is merely translated by the poet into art. After many readings, I still enjoy it, and have never considered, before now, to gaze so deeply into its depths as to invent a secondary meaning.
Conversely, with a poem like "Ozymandias", also by Shelley, the ambiguity of the poem really rather invites the reader to reach - irritably - after the many facts and reasons of it.
This has turned into rather a long post, in which I've rather raved about a great many things which hold little to no interest in me. My question has been answered - evidently, Realism and Art can coexist, therefore I would believe that Poetry is not exempt, as long as it is art.