Yes, he is the best in the world at that one dimension but below average in virtually all other dimensions. He's only gotten 'better' in recent years because he used to be absolutely brutal before, especially defensively.
If you want the clearest sign of his decline just look at his goal to assist ratio, 50 goals but only 21 assists? He wasn't even PPG last season... The guy now waits for the game to come to him most of the time, any neutral observer without Ovie blinkers on could tell you that there is a pretty big difference between the guy that you see in 2015-16 and the Ovie of 2010. He's become overly-reliant on his one trick as his other tools have decreased, it has maintained his goal ratio up but other parts of his game have clearly deteriorated.
His numbers are decent in the playoffs, but he's never come up clutch and has no post season defining moment. Never even led his team out of the 2nd round. And he's 31... Maybe it's his leadership that needs to be questioned, who knows, but it's clear that an Ovie-led team is simply not going to get it done at this point.
This article from last year is pretty damning, and I can only assume the pressure has mounted significantly for the only multiple hart winner in history to never experience any post season success:
http://ftw.usatoday.com/2015/05/ale...made-conference-finals-hart-trophy-statistics