I think it's unlikely that players just laze around like people suggest unless they have come through our youth ranks perhaps. I find it really unlikely that someone with the drive to become one of the worlds best players (as in the top few hundred out of the billions of people on this planet), just gives up when they get a competitive game.
They are perhaps not good enough compared to the others that made it to this level, they try too hard, find it hard to get a partnership going so balls go one way when the partner player goes the other (this is particular makes players look worse than they are), not coached strategically well enough and a number of other possibilities, I do however really doubt that a genuine lack of heart and effort are a part of it.
Generally the motivation will be career rather than club, but that is still just as big a driver for many. Wanting to play well enough to force a move to the real big payers like City will be a big force as well.
Our biggest problem is a lack of understanding of the movement of each others game to be honest. A 5 yard pass doesn't reach it's target more often because the intended target has run in a different direction, than because it's passed badly for example. It's the passer that gets the grief though. This is the same all over the pitch. Strikers make runs that don't get picked out, midfielders do through balls that don't get run onto, defenders pass players on who don't get picked up and so on.
I think they play with passion, it's just misplaced and often obscured by a pass being misplaced at the end of a run.
Not to say we are not playing like donkeys mind. Just I don't buy the lack of heart and desire argument, if they didn't have it, they wouldn't be premier league players surely?