If you watched him play a lot this year this isn't that surprising. He was a shell of his former self and the Lions basically just used hiz size and the threat of what he used to be to get him open on curl routes.
TBH he's been declining for a few years now, which has mostly just been masked in the statistics by the Lions throwing 50 times a game or whatever.
At his very peak I think it's hard to argue that he wasn't a top 15 or so player at his position, but the injuries caught up with him, and his stats were always inflated by playing on a consistently losing team that was forced to throw the ball too much across his entire career.