That is obviously true, but they dominate possession because of their approach to the game, which means that they don't need destructive midfielders. Guardiola defends with his front players, with his wingers, with the whole team. I know that not every team can necessarily play that way, I've just felt for a long time that the DM position is overrated, and some of the players that play it are overrated.
Another example is Kovacic. He went to Chelsea having made over 110 appearances for Real Madrid in three seasons. Any other player that had done that and signed for Chelsea, not only would it be a really exciting signing that would capture the imagination of fans, but you would really expect something from them. But Kovacic made almost no impression whatsoever. They could have got someone out of the Championship, and he couldn't have done much worse. Now Kovacic will get to move to Inter Milan, or so it seems, after 4 seasons in which he scored 3 goals in 161 games, and for Chelsea he had 1 assist and 0 goals in 51 appearances.
Now I would say that player is easily replaceable, and if you signed any other major first-team player from Real Madrid then their contribution would be far more obvious and explicit. I wouldn't say that anyone could 'sit in the front of the back four', but you don't seem to have to do that much if you do play in that position. All you have to do is not go forward, get in the way occasionally, and recycle possession. That's all Kovacic does and has done for years, and yet he's considered world-class in his position.
a little bit of a luxury player. If your defensive strategy works, he's great. If he's got to improvise, cover a lot of open space and finds himself in many duels against attackers, of course a 'typical' DM is better. Think he'd be great for City exemplarily, just as he was for Napoli.