I don't have an issue with our defensive line depth, it suits our defenders and allow us to not concede many occasions. I have an issue with both transitions though and I think that the problem is about coaching more than tactics, our midfielders and attackers seem to not understand the concepts of cutting passing angles and containment, they seem to only know two concepts tackling and getting to the theoritical spot in the defensive setup, good defenders also know how to get to that spot efficiently which means slowing down the opposition while retreating. An other thing when you have a deep defensive line is that your forwards need to backcheck, I like hockey concepts in football because both games are tactically compatible, in this case backchecking means that the attackers and attacking midfielders apply backside pressure instead of the popular forward pressure.
Now when you play with a deep defensive line and often regain possession in your own third, you need at least one player that is very good at moving it into the middle third. I like to call these players washing machines, the likes of Fabinho, Fernandinho, Busquets, Carrick, Pirlo, Modric, Scholes or Verratti, you give them a dirty ball and they give it back cleanly. I don't remember Pogba ever being good at that, at Juventus that role was either played by Pirlo or Marchisio with Vidal and Pogba ready to receive the ball in the middle third, Kanté does that for France today and Cabaye used to do it before that.
Also I mentioned it more than once but one of the reasons Pogba isn't good as a 10 is because he isn't consistently good with his back to goal whether it is in his own third or in the opposing third. He thrives when he has the game in front of him that's why I don't consider him as The engine of a midfield.