They're not unfit, the system is just ultra defensive shit so they need to run more to cover gaps. Watch Man City/Bayern/PSG/Madrid, even Arsenal, and see how close the players are to each other, the strikers and wingers play really deep and come forward together as a unit. If they lose the ball, either you have to thread a perfect ball through a packed middle or hit it hopefully over the top. Our midfield is really dispersed and our defense often gets no proper cover so lots of midfielders are sprinting back and that's why we get tired easily. When we attack, there is rarely any midfield support because it's usually a long ball to the striker and then we fumble around until we create something. Man City players walk the ball forwards and they sprint forward in bursts, creating space but they always have someone close for support, they always have lots of players in the box for a rebound too.
You don't have to sprint around the pitch, you can be smart and cover gaps by having the 2 or 3 nearest players press the opponents as opposed to religiously making a 5-5-0 shape off the ball. It looks organised but when you need to attack we have to all burst forward because we always start by hoofing it up to the strikers hoping they hold up the ball while we try and support, then if we lose the ball, everyone has to sprint back to 5-5-0 and we're tired. That's why Dybala and Chiesa were so important to us, they linked the midfield with the forwards so well and we don't have anything like it now. Right now, we should play a 3-4-1-2 with someone like Miretti or Fagioli in a playmaker position. Max always complains that players are out of position but that's dinosaur football right there as we're often in this rigid structure that even Maccabi was able to exploit and pull our players out of position with just 1 or 2 extra runners. We play very much like a park-the-bus team when we don't need to and even then, we give up a lot of chances.
Fossil football tactics by Allegri are similar to Conte, watch how Spurs play shit football all season but get bailed out by their superstar forwards. It's nonsense saying our players are lazy and unfit, they'd be dropped immediately and never get international minutes. You've got to have Neymar talent to get away with being lazy. Just watch Napoli and how they play and how they defend and attack collectively, it'd be an education for Max given that we have a squad that could play that type of exciting football.