Wdym? Shin has always struggled with anything intelectual. There has never been a time or arc in which he had overcome that weakness. Of course it is stupid, he IS stupid. The only "wise" part to him are his morals, but he can't even really put into words those ideals. Just look at the very recent arc with Kanki, just how much he is struggling to try to make his mind about the whole situation. This is pretty natural to his character.