I see many people who say Erling Haaland disappear in the field like you say, because they think Haaland is not suitable for the games against stronger teams and that's why people think Haaland is just a player who can have good performances against the teams with a weak defending system, while he is not because other teams usually focus on Haaland to make this player stop.
Erling Haaland has been ghosting in important games and it's becoming disturbing because he can't win prestigious awards with this types of performance. The game against Newcastle was an important game and he got the lowest rating. Newcastle united currently is one of the best teams in the premier League and they have the best defense so instead of supporting Erling Haaland ghosting against them, he should be criticize so he can improve his games or very soon all his goals won't get him anywhere. We have good goal scorers but that's not what football is all about and that's why Messi is still been favoured over him for the Ballon D'or discussion because Erling Haaland has wasted all the opportunities (Finals) he had to prove himself.
I do not know what influenced Haaland performance to decrease this season whereas last season he had a very good performance and was able to score very many goals in the EPL. it makes sense if you say that Haaland is not suitable for matches against stronger teams because in the UCL final at that time Haaland could not do anything even other players who were able to perform well scored for Man City. I also agree with what @CryptopreneurBrainboss said if Haaland seems to need to be criticized and given an evaluation of his mistakes in the match against Newcastle yesterday so that he knows what mistakes are so bad that Haaland performance is not optimal and this will be a tough task for Guardiola to know about Haaland problems and get him back to being a high ranked player again because otherwise its likely that Haaland will still have a poor performance rating until the end of the season.
on the one hand Man City still has ambitions to get a trophy in the UCL and if this flagship player cannot improve his performance immediately I think it will be a little difficult to get another UCL trophy.