Our tactics are all wrong.
Slow motion lethargic displays won't beat a pub side, let alone a strong European one in EL semis.
It's not necessarily the formation, though it does play a role, it's more the tactics. For one, our players are always maintaining the exact shape in attack. It gives the defence nothing to think about, as you always know exactly where your man is going to be. If this wasn't bad enough, our passing is so slow that it's almost in rewind. Again, it hardly threatens the defence. To make things worse, we have all but given up on pressuring the opposition as a team when defending, we just hang back waiting for them to get real close to the box or give the ball away.
Conte needs to mix things up a bit, if not in formations, then at least in speeding up plays at times and allowing players more movement in attack.