On the other hand, you have other developers that check here from time to time (From the top of my head, Caz comes to mind. Maybe because their game was the most recent one I played) and if those developers who develop quality game content think highly of your work and appreciate the effort you put in then that's more than enough to show that you're headed in the right direction.
I can't understand your frustration because I've never been in that situation before but being angry for your friends is a good thing.
Reminds me of that news when a student destroyed their artwork due to trash tier criticism (not constructive). Honestly, it's best to just disregard their comments as much as possible but if you can't, just think of the good feedback from everyone else.
I find your artist's work very cute and that level of art is on a level I can never attain in my life even if I tried to (stuck with drawing pikachus for days) so they should hold their head up high and be proud. =)