You misunderstand. Creating art is hard. Putting oil paint on a canvas is easy. So if you pay money for paint on canvas without any other checks you will get the simplest passable form of paint on canvas. If you don't mandate that the whole canvas is covered all you will get is a pile of canvas with a single brush stroke.

Look up the concept perverse incentive, or cobra effect: https://en.wikipedia.org/wiki/Perverse_incentive

As I wouldn't want every local governmental authority to freely define what constitutes "art", it means that everything can be categorized as art.

So the most economic and democratic solution then is to close the whole circle and reduce tax for everyone in return of submitting "art", even if it's just a picture of a milk-carton in a corner.

However, the consequence would be excessive governmental cost for the Ministry of Culture and Arts to preserve every piece of contributed art, so every citizen can see every art created by every other citizen. This of course would have to be funded by tax-money, which unfortunately means increased tax-burden for everyone...

Result: A development put in motion which will definitely not end up prioritizing people being paid to create art!