You might think that translucency is a good thing in a watercolor, but not in gouache. Versimilitude might be good in a portrait, but not in an expressionist landscape. And so on. On the other hand there is a logical (or with a stretch a "metaphysical") attribute that all good paintings have. They meet the criteria for excellence in paintings of that type. Helen Knight on the use of "good" in aesthetic connections is brilliant on this subject.
I haven't read the Fried piece, but I do see that there is an obvious objection to "theatricality". The objection is that it is phony and therefore cheap. Or one could go further. One form of phoniness is insincerity, another is sentimentality. Consider for example the difference between Rembrandt's sketch of "A Young Woman Sleeping", in the British Museum, a modest but tender sketch of his girlfriend, and Käthe Kollwitz's brilliant but melodramatic sketches of mothers and children. I am not sure whether the objection is completely overwhelming, though. Herman Hesse's Glass Bead Game, for example, is theatrical.
Most aestheticians make the distinction between aesthetics and philosophy of art, with "aesthetics" being the wider term and "philosophy of art" the narrower one. "Philosophy of art" is only the philosophy of works of art or art objects as they are unappealingly called these days. In other words, these philosophers accept that it is not only works of art to which the terms of aesthetic appraisal apply, such as "attractive", "unattractive", "lovely", not lovely", "unlovely", "majestic", "grubby", "oily", and on and on, without end. They also apply to the human face and the human form, to nature and parts of nature, including natural landscapes, the sea, etc. There is practically no word, I believe, that cannot one way or another be used as a term of aesthetic appraisal. The aesthetic is everywhere; a happy thought.
"Let's agree that something is art if the art world views it as art." I think that we shouldn't agree to this proposition, precisely because it does seem that it has the relativistic implications you describe. So I take your question to be, "Does the institutional theory of art, e.g. George Dickie's (the theory that something becomes art if and only if the 'artworld' gives it this status) have the implication that something can be a work of art at one time and then not be at another?" The answer the institutional theory gives is that it is the totality of all the little artworlds at particular times and places inclusion in which at any time makes something art. Does this answer work? Does it make indeterminate today whether this is a work of art, as whether it is seems to depend on the possible response of some future art scene. Some ugly Greek pot is displayed in a museum by lovers of Culture today, so it was art even if the people who saw it at the time it was made dismissed it as crassly commercial or just ugly.
There is the fact that it is possible to treat something badly or to damage it, whether or not it is sentient. A pair of shoes can be badly or well looked after, and it is wrong not to look after a good pair of shoes properly. A living thing like a hedge can be properly maintained or attended to, but something more is involved. Sometimes, it seems to me, the aesthetics of the "art object" (horrible phrase) can reflect what it actually is. So it is natural to trim a box hedge in one way, and a mixed hedge in another way, perhaps a less formal and more undulating, the shapes reflecting the different kinds of growth - hawthorn, or privet or beech. (A hedge that is full of straggly and unwanted sycamore looks awful, and the holes soon begin to show.) Pugs and poodles may be perfectly happy qua sentient beings, though often there are specific health problems with specific breeds, but it is perfectly coherent to object to the whole process of breeding and thinking of living things as being objects for our use - manipulation - and enjoyment only. Much the same comments can be made about the wilderness, and your question and suggestion raise profound and important questions of ecological ethics and aesthetics. For some, the ethics of GM foods has a spiritual dimension too.
My answer to this is a firm "Yes". Novels, for example, "tell the
truth" better than any other written material, with the exception
things like diaries and letters, unless you think of the relevant
passages of diaries and letters as though they were mini-novels. But
diaries and letters are no better at telling the truth in the
appropriate sense than the skills of their authors. What sense is the
sense in which novels (or more generally imaginative writing) can "tell
the truth" better than any other "Areas of Knowledge", as you call
them? (I imagine that you might have the sciences in mind.) The sense
is one in which telling the truth has to do with getting the details of
a description absolutely right, and getting the overal balance and
colour and mood of what one is describing absolutely right. Here
psychology for example (which might be thought to give "tell the truth"
better than the novel) is no better than the sensibility (the
eighteenth and nineteenth century word) of the individual working
psychologist. And psychology as a whole can be worse, because its
collective or institutional scientific structure blots out the most
personal and individual aspects of its subjects' lives. 'What an
intelligent man knows is hard to know', as Goethe observed. But I agree
with Kalynne Pudner that there is a rich and rewarding philosophical
literature that exists exactly on this topic. My philosophical guides in
the area, who share the view I have sketched above, are Iris
Murdoch and Vladimir Nabokov.