I don't really know enough to dispute this, but this statement is setting off alarm bells as a thought pattern that would be easy to fall into but hard to falsify. Most artistic output in the world is mediocre and irrelevant. Seeing the same from Belgium is not enough to say the policy is not working.
Belgium has about the same population and GDP as Ohio. Genuine question: how does the "artistic output", however you want to measure it, compare between Belgium and Ohio?
Note that I am not claiming this is any way "worth it", especially with your comments on the middle class which seem to be echoed by other Belgians. I'm only asking about the actual artistic output in isolation.