As mentioned above, a delusion ("My works are flawless masterpieces that everyone loves!") would probably cover this, perhaps combined with some degree of Overconfidence or Megalomania. Add in the Incompetence quirk if you think their rating in the relevant skill isn't low enough.
If they're
genuinely neurologically incapable of recognizing their own flaws, you might also want to build them a Neurological Disorder for
Anosognosia.