It wouldn't make sense for Coke to change how it tastes and then ignore feedback (or only listen to the positive feedback) and I don't see how that's any different.
This presumes that the motivation of the artist is to profit from their art. Many artists create simply for the sake of creating, occasionally allowing interested parties buy commissions in their style for the sake of it being their style.
Certainly an artist who is interested in broadening their appeal will ask for critique when they are ready to accept it. If they don't, it's not your or anyone else's duty to wave it in front of their face. It's their loss if they can't find enough work.
This presumes that the motivation of the artist is to profit from their art. Many artists create simply for the sake of creating, occasionally allowing interested parties buy commissions in their style for the sake of it being their style.
Certainly an artist who is interested in broadening their appeal will ask for critique when they are ready to accept it. If they don't, it's not your or anyone else's duty to wave it in front of their face. It's their loss if they can't find enough work.