I feel like judging how many goals you concede depends on how good your CBs is a very 90s or early 2000s idea.
In short, Pep's Bayern or Barca sometimes don't even play with any CB, and they didn't concede many. That is just an extreme example, but the point is there are so many moving pieces to dissect the defense problem into this. Like the lack of a threat in attack, the more willing the opponent is willing to throw bodies at us.
2 out of 3 CBs have some huge decline individual performances, and I am not referring to plays that has external factors affecting them, like who was pair on the side with them etc. I am talking about ariel duels, toughness on the turn etc.
Obviously, it doesn't help that Inzaghi set the team up in the objective of outscoring the opponent, but if we have the right attackers (budget), this might not even be a concern for us, e.g. killing off the game 3-0 half time, or just plain outscoring them with better conversion rate strikers etc.
Also, I believe one of the reasons we have to over commit with players in our attacking phase is lack of those individual brilliant players, like imagine we have G.Jesus or Vinicius Junior instead of Correa. I doubt we need our CBs to involve in the attack play this heavy, or the risk they need to take, or we would've scored more already.
Sorry didn't realize it is the Lukaku thread and the post above me.
Just want to say the discussion above was wonderful, love reading them.