Any time you’re discussing art and art theory, you need to consider the audience. We all carry different lenses with us that affects how we process information. Despite an artist working in a realist method, the form could still be distracting to the viewer. A formalist artist could create a piece of work that someone would call kitsch. A post-modernist’s work could appeal to someone who is troubled or angry at the world.
But in all fairness, I can see why each theory has it’s following. Realism and expressionism are for people who fall into the mainstream of society. Realism is favored by those who enjoy things on a surface level. Not necessarily in a vain sense, just in the face value sense of what you see if what you get. Expressionism is the embodiment of an artist’ emotion and how the piece makes you feel. That’s why a picture (artwork) is worth a thousands words – you can express yourself when words fail you.
Formalism and post-modernism are for the outsiders and the protestors, respectively. Anyone who is a follower of an art-form with the goal of breaking away from kitsch, as formalism does, wants the open arena away from social and ethical issues. Similarly, people who deliberately embrace work that challenges or goes against notions of beauty, as in post-modernism, want to because it’s counter to what society does.
Everyone has their own taste, I would hope that one day we can be better at agreeing to disagree.