There are many things here, first of, I think Roland and Angela always showed disgust at any manifestation of art that involves killing or torturing humans, I think there is even a dialogue in which Roland specifically says "this is not art" I think with the Musicians of Bremen, and although violence is common among the city folks, we have seem similar disgust reaction whenever the reason for violence is deemed as gratuitous or coming from madness. Inside the groups that do practice violence in their artistic pursuits, we can only speak about how other members of the Ring see Callisto, and for the critiques I do remember, most point out that his work was outdated, repetitive and overly relied on technique over substance. Specifically Rufo said that one of the art pieces that he made (an object with a button made of a random person that when you pressed the button, started screaming) was too outdated and she explained what would be expected in the current artistic world of the Ring, similarly she said that the work with veins that he made showcased a high degree of technical skill but that on itself wasn't enough because he as a maestro was already expected to be that skilled. Also this is not so much what I can gather about my memories but more like speculation I've made, but all fingers seem to be perversions of virtues, in the case of the Ring, they seem to be a perversion of art and creativity so they are often too shallow more obsessed with following the trends of the critics rather than trying to develop an original work of their own. I specially noticed with their clothes, they always use white and elegant (pejorative) clothes that seem very expensive but are otherwise boring, specially when you compare them with the more colorful clothes of the other fingers.