I must admit that I didn't see the game on Sunday so I don't know just how little effort he may have put in but in the role that Shinnie plays in it's not his job to go charging all over the pitch closing men down. I don't think that is a particularly fair stick to beat him with. That said, I do agree that he has been very much under par. In recent games, such as against Hibs, he did show quality but also seemed to spend a lot of time on his arse after falling over himself.
I'll be sad to see him go, he's a quality player, but he has been very subdued ever since the 3 - 0 Aberdeen game in January only occasionally showing what he is capable of.