As a fellow ret I feel your pain around this.
My tip is to try and organize it together with some friends since actually getting into a pug run as a ret is very hard since we are not amazing for it (but people seem to think we're a lot worse than other classes, even though we are not).
I think this problem mainly comes from challenge modes offering very little replay value once you have done gold, hence getting a group is really hard in the first place. Not sure how to fix that.