After the 2-1 score and Milan red card, Napoli launched a devastating attack, nearly overwhelming the Milan defense. Fortunately they held on until the final minutes and secured three points, even with only 10 men.
I agree that Lukaku role is irreplaceable, and Hojlund hasn't been enough to sharpen the attacking line. The top five positions are still very volatile, as the margins are slim, and they could still change if each team can't maintain their consistency.
There's literally been no record of consistency for Napoli IMO. When a team doesn't provide every player with their matchable replacement, that's what they get.
Ac Milan had majority of the control throughout the game, which made Napoli struggle through just to keep possession. The very first goal was avoidable, but because of a weak defensive strategy, they could not fall back in place to keep the ball away. I also loved the last sway kick from Neres in the last minute; didn't do too much harm from that angle, but it would have been a record breaker if it were a goal. Napoli needs to sit up seriously.
Napoli faced a team that is resurgent and that is objectively strong under the new coach Max Allegri and they did all this at their home, everyone knew it would be a difficult match.
Milan played very well and Napoli suffered because they found themselves against a strong team but they played quite well, I understand that you didn't expect the defeat but to say that it's over seems excessive to me.