Haaland did a great job to make Manchester City win a title.
Haaland didn't make Manchester city to win a title, rather it was Manchester city that made Haaland to win a title. Manchester city is used to winning titles while Haaland wasn't used to winning titles until he joined Manchester city.
Exactly Haaland is not a key component for Manchester City’s success this season, even without him, Manchester City will win the league because he was not the my important player in the squad.
Last season, I will agree with @Rebekker that Manchester City’s success depends on Haaland goals because he was the main man in the squad that score the most important hold that determine their success in their last season’s Premier League championship.