He's a support, which is one of the lowest picked roles in the game. You become completely team reliant. Solo carry games are few and far between anyways, but still...
He can't gank lanes with no damage because he brings none himself.
He gets a free enemy camp every time his smite comes off cd, but any fighter jungler can just take ALL of Iverns jungle because he can't fight back, or even last hit with smite.
He has no reliable escape if the jungler tries to come for him, unless he Qs a camp.
He has to have Daisy to get dragon alone, and even then it takes FOREVER, most of 2 bushes, probably a minute and a half. He has zero potential to fight anyone who comes to get him and no way to escape if hes on blue side.
His W can be used against him, and isn't really THAT powerful of an ability.
And he has zero waveclear, something I've come to love on many of my picks. The ability to delete a wave and go be useful.
Basically people learned how to play around his gimmick and he lost all of his early game power. In a 'protect the carry' comp hes okay, but why wouldn't you just pick a tank?