What is Art
Art is the representation of a thought in the physical world. The artist themself chooses how to craft the idea such that others might be able to experience it accurately. Because only the artist knows the thought behind the art, only they can decide whether or not they were effective in their expression of it, therefore only the artist can say whether their art is good or bad.
It is common for individuals to seek to judge art with their subjective opinion and parade it around as an objective one. Most people feel their subjective opinion is worth less than those of others, and will therefore adopt the existing collective subjective opinion as though it were an objective one. This of course is an inherently flawed way of receiving art because we give power over what we subjectively perceive to be the objective universe to a few subjective perspectives.
If the art was created with a defined purpose, for example with the aim of making one thousand people happy, then we can objectively judge whether or not the art was effective in that we can compare the number of people the work actually impacted versus the target. We can then use the words good or bad in relation to the goal, but still a scale of efficacy is more semantically accurate in that it does not imply quality which is again subjective.
Art created for the sake of art is abstract in that it serves no extended purpose other than existing as the representation of a thought. Therefore the style and medium used are entirely up to the artist and cannot be measured against existing styles and mediums considering that both are human creations and not based in any universal truth.
Though conscious thought is a product of nature, the products of consciousness are one degree removed from it in that the consciousness can observe nature and intentionally invent abstractions separate from it. This adopts the view that the distinction between natural instinct and human creativity exists simply because of the ability to express the distinction. If however free will is an illusion, every thought can be defined as being the direct product of compounded natural instinct and therefore any notions that it exist separate from it are also illusion.
The most accurate definition of art, from my subjective attempts at forming an objective definition, is this: a representation of a thought from one subjective universe into the mutual objective universe which other subjective universes can experience if exposed to.