I don't know if this counts as an "Art World Sin" but...
Fucking.
Tumblr.
Nose.
THE MOTHER FUCKING "TUMBLR NOSE" MAN. Holy shit. Red fucking noses EVERYWHERE. It's like every fucking, mother cock-sucking, colored drawing of every character in existence nowadays has to look like they have a damn cold like it's "rudolph the mother-fucking rednose reindeer flu season".
But hey, it's tumblr. Where everybody's a mother fucking snowflake and every made up gender with a name that sounds like something a snart blender upchucked is illegal to disprove/call out or they'll "like totally report you for gender discrimination" and call all their tumblr friends for back-up so they can help nuke your blog with no warning whatsoever.
Oh and the ones where they keep trying to draw any canonically skinny/slender/slim/sexy character fat/obese, because "that's not real beauty" or something...
That shit's horrible to art too.