Why has Lil Wayne Fell Off?

CArter I was when he stopped sucking ***.... I remember the Clic that was the CArter II, which included greats like Tha Mobb, Hustler Muzik, Fireman, Money on My Mind, Shooter, Fly in, Fly out, Mo fire and other greats...Then he came out with Dedication II,which was solid with tracks like GEt em and Welcome to The Concrete Jungle, then the Drought 3 was a beast with countless renditions of good songs (Moment of Clarity, Live from the 504)..and then bam, he started gueswt starring on a bunch of songs and he was generally weak (except on the Shawty Lo track) and then Carter III just sucked *** with relation to the Carter II and the Carter I, I only count 3 sogns where he has done well on in the last year (DEy Know, Im cold, Lost) and I just want to know informed opinions about why he has fallen off so heavily ?