Except he couldn't perform when he was younger. He failed at all his many loan spells except Pescara, and that was Serie B. And proceeded to fail in Sevilla and Dortmund.
It's ok, players develop in different phases, he wasnt shit then, now the is the shit when it comes to being a pure brilliant finisher. It is what it is, he is in the level he deserves to be. He turned 30, so I'm not sure he wanna risk another big move that might not work out again.