He's still a good passer and probably still one of the best around when it comes to handling the ball in packed spaces, but his dribbling stats are absolutely abyssmal this season. Probably because his acceleration went down the drain, which also limits his defensive impact, despite him usually covering a lot of ground during matches.
If he had decent athelticism he could probably be a pretty great CM, but since that's not the case he needs a fairly specific tactical context to look good. He's still a very useful player to have and Dortmund were very open to extending his contract (just not for the supposed €10m p.a.), he's been quite effective as a false 9 last season (7 goals, 7 assists in 1675 minutes), but he needs the game to be closed, his team to be camping in the opposition half, with him moving around, dragging defenders, shielding the ball and making himself available for quick 1 touch combinations.
Inter has been rumoured to be interested in him for months now. Hertha apparently, too. But he's always been such a high profile figure in German football (irrespective of his performances) that I have a hard time picturing him playing for a bland midtable side. Not to mention that most of those sides heavily rely on Klopp-like pressing, which he isn't up to anymore.