I haven't watched his latest performance, but as a 6, he does have influence on the defensive side of the game. The guy isn't afraid to be physical in that position possibly because he gets to crash in from behind.
But while in possession, I don't share your opinion seeing as you're bringing up the Silva's in possession. As long as you can stay tidy as a 6, it really shouldn't be a problem. It might mean he won't get to dribble (riding tackles), but that is just a very small portion of the dribbling a 6 can do. He can easily carry the ball with space, and can easily use his dribbling skill to shake the defenders off him like in that twitter video of his performance vs Nantes.