I think City being a great team plays a good role on this as well, Haaland is amazing but you can't put Haaland at a team like Everton and expect him to get the most goals in a season, that would not work, they do not get enough scoring possibilities.
Of course you are correct Haaland is a very good player, he is one of the first Bundesliga player to come English league and perform the way he does, he is actually one of the best striker on premier league that scores almost all there matches.
There is no doubt that Haaland is one of the best strikers in the Premier League if not the best because he score plenty goals that people never expect in his first season in the Premier League, but this season, he has played some matches without scoring goals due to the absence of KDB in Manchester City's midfield.
However like you said Haaland can never be at a club like Everton because his chances of scoring the way he does on Manchester City will no longer be there because his performance was dependent to the kind of tactics Manchester City has so going to Everton may be very difficult for him to cope.
You are right! but Everton style of play can be favorable for Haaland as well because they play a long ball pattern which is what Haaland is after so that he can be scoring ball from crosses.