Eminem's songs do have concepts... they are just becoming generic. The controversy thing is just his signature. Most rappers have one... for example Rakim has heaps of different songs, but each song has a trace of battle rap in it where he self-glorifies. Em's signature is pissing you off while getting a message... but he is becoming generic. He's getting filler concepts in like "Soldier" and "Without Me" which have all been said before, by Em himself or some other rapper.

^ and THAT, is why he is falling off