Tracy Morgan is not funny....anymore

I used to enjoy Tracy Morgan on SNL. Now he talks and acts like hes mentally challenged. His Stand up is trash and not funny. How can he go from talking normal and being funny on SNL, to what he is today? Every interview hes done on Howard Stern is painful and not entertaining. If you go back and watch some of his old skits, hes seriously funny and talks normal. Brian Fellows and Woodrow are great, what the hell happened to him?