That's the trap in which some of you seem to be falling. Art is already defined as you and others have pointed out.
What I'm saying is that the benefit of *absolute* doubt need lay with the artist, never you. It probably cannot. I'm saying that we need to acknowledge that fact, encode it in our definitions of art, if it isn't already, and teach it, so as to uphold and further its integrity for art, artist and culture.
Free it from the "elite".
If the artist lives on a planet and makes a work that positively *everyone* on that planet claims (some through media brainwashing) is not art, that still doesn't necessarily mean so, contrary to what some might have them beleive. Hell, the artist might have a higher-intelligence or creativity-mutation, or their work may appeal to those on another planet who do get it.
The artist's claim shall trump or supercede all others. If a tree falls in a forest and there's only one person to claim to have heard it, does it make a sound? What if everyone decides that it did not make a sound, despite the witness' insistence?
"Ought to" and "Should be", etc., seem like less-than-virile arguments.
I'm tempted to reject skill as a prerequisite, due to cave art, folk art, or art that is composed by those who, *according to some*, have "less" skill or different motor or conceptual capacities than others, yet want to still create sincere, soulful, spiritual, communicative or otherwise truthful artwork. That sounds like you're proposing a form of elitism-- art guilds and art-critics and whatnot. An industry.
The injection of the kind of criteria you seem to be suggesting seems to muddy the matter beyond helpful. The cure worse than the cause.
You know, over the years, I've found myself questioning the whole matter of what we see or call culture (which of course includes art), and I've been forming a contention that what we see as such may be a kind of illusion, merely the tip of an iceberg... Backstreet Boys, Michaelangelo, art guilds, Martha Stewart Living, Oprah, The Gap, Survivor, McDonalds, NBC... Salient culture served up *as* culture. Culture as defined by elite groups. As some have complained, often the loud, aggressive, self-absorbed, officious, obtuse, power-crazy or ruthless.
By that perspective, every culture in the world is a form of illusion, and that the biggest, perhaps truest, culture is that which holds the top up, and that is below the waterline, less seen, unless you're willing to sail up real close and take another look.
75 years later, a car is art.