Whoever the player is, if they encounter a strong defense then they will struggle, not just Haaland. Looking at last season, when the club faced Mamchester City, their defense received special instructions to guard Haaland, and it worked a lot. But Guardiola's clever use of other players to be the second target after Haaland and proven when he struggles to find space because of tight guarding other players who create goals. Now here we can see good teamwork.
Guardiola has a lot of attacking players in the team and many of them have leadership qualities that allow them to take responsibility and therefore it is not so easy to restrain each of these players. Silva, De Bruyne, Gundogan (no longer in the team) could create the chance themselves and score a goal, the value of such players is very high and this allows City to have an advantage. Haaland is a very talented striker, Guardiola could see that in him.
Because basically, Guardiola is not careless in building a team, because Guardiola also really considers substitute player who have good quality too. Thus, when there are injured main players, at least Guardiola will be able to rotate and implement the right strategy for Mnachester City according to the existing players.
So yes, don't be surprised when some of Manchester City's main players get very tight guarding by the opposing team, but in the end Manchester City can still win the match. Also for this season, of course Manchester City still has good quality also in the Champion League, so Manchester City still has a chance to reach the top match in the Champion League.
The thing is most of the opponent that Manchester City are going to face, actually knows how to stock Manchester City. But that does not mean it is going to be easy to actually stop Manchester City. Of course Guardiola also knows that very well. So he will try to change up the tactics as well. And another thing that we have to understand is every player is not going to perform well in every match. So it is also not very realistic to ask for a great performance from Haaland in every match as well.
Anyway, I think Manchester City is definitely going to be consistent. At least consistent enough to win the English Premier League title.