This season Haaland has played really well, but indeed he hasn't been very good this season in terms of fitness. He's been very injury prone this season which makes it difficult for their form this season.
Their performance was erratic as Haaland's condition did not improve.
Now there is new ammunition to replace Halaand who incidentally Haller is also actually quite good in the Eredivisie but indeed it is still quite difficult for them to compete if there is no motivation there.
Dortmund had a really high chance of tying Bayern Munich for the league title last season. However, the problem was they relied too much on one player, Haaland, and when he was injured they had no one to turn to.
This mentality needs to be changed otherwise, they will not be able to perform at the highest level, not even in their own league. No matter how much we talk about the Bayern Munich competition, it doesn't matter. There is no need to emphasize how any other team in the league could become a serious competitor for Bayern Munich. However, I think we all know that Bayern still does not have any credible competition. I am quite certain that they will win the league title next season as well.
Duke
Now Haaland is gone and indirectly this will actually be very good for Dortmund now because they inevitably have to make something new and don't make another backup for now even though Haller can also but it would be better if not too dependent on one player .