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.