Having a legit #1 WR can change the entire dynamic of a game. Currently, there isn't a single receiver on this team that gives defenses and DCs fits. DCs don't have to adjust their gameplan because they are scared of anyone going off and taking a game over. Additionally, the attention of a #1 WR helps other guys get open because of the way the coverage is.
Shakir is a nice player but he is more of a complementary piece. He'd be even better if we had someone on the outside who could actually draw attention from the defense and get open downfield. That should be Beane's focal point this offseason imo.