In this match there were actually some controversial refereeing decisions that were actually detrimental to both parties and maybe the disallowed Milan goal was one of them.
Football rules these days seem to have changed, because lately there's been a lot unaccepted, inconsistent and controversial football decisions from the VAR and the referees. Decisions are now very unpredictable, i don't know if the people to blame are the ones who programmed the VAR machine or the machine itself, something has to be done. Milan pressed hard in the game, but it seems Napoli kept a high defensive line because Milan were offside a couple of times. I feel some offside decisions were correct, while some were not.
With VAR, in fact, sometimes there are advantages and sometimes disadvantages because this is a machine and a machine sometimes experiences errors and this is what makes VAR a lot of opposition.
the rest is about human error I don't want to talk about this because if you see and explain it will be very difficult for most fans to accept.
but on the other hand VAR should be able to help the referee but what is happening right now is a lot of controversy there.
The rules contained in true football are that it must be renegotiated again because there are some that do not match the reality there.