You ignore the power of "and" - the work that a handful of people love AND that everyone else on Earth agrees is okay, AND that some people find horrible...
If someone said that if there was NO financial motive for art, there would be no art, you'd tell them they were being silly - some people will make art without any financial motive. And you'd be correct.
But you seem to be saying that as soon as one gets any recompense for art, all their art becomes of no value, made for the lowest common denominator - and that's just as silly, for exactly the same reason. Ergo, financial motives are not a death knell for art, in general.
For our purposes, financial support from art increases the opportunities to create art. If artistic creation means the artist doesn't have to spend their days sorting recycling, that means they can make more art! And, until we are in a post-scarcity world, the way to keep the artist from sorting bottles and cans is to pay them for their art.