City just won the league without a 20-goal striker and their top scorer was Gundogan with 13 goals. They also had only two players with 10 more goals and ended up scoring 25 more goals than us overall.
If our attackers chip in with additional 5-10 goals at the very least, if the midfielders and wingbacks can chip around 5 goals, then it's not impossible to challenge for the title at least.
Even if we get Haaland, we can't expect him to be the only one to score the goals. Others also need to increase their output. And have said this long before, not sure how realistic is it as well to expect a 21-year-old to come to the Premier League and immediately lead a team to a title win/challenge, freak-of-nature or not.