How can art reflect values?

If art is believed by an individual as a reflection of values- then how can it do so when humans are not omniscient? People cannot know evertying pertaining to reality and metaphysics,so wouldn't an artist only be able to construct the facade or phenomenon of values. If the artwork doesn't represent the values (as the art is meant to) doesn't the purpose of the art not exist? Is art nothing more then improper attempts to tell meaning?