Even having Erling Haaland wasn't enough for Dortmund to reach a championship in the Bundesliga and their job will be even more difficult in the absence of him. Dortmund are going to have only Moukoko and Malen after Haaland's departure. Moukoko is only 17 now and I assume that Dortmund wouldn't like to put Moukoko in their starting eleven. Malen would be their first choice. He is a capable striker actually and he is young now too (23). But I'm doubtful about if he can do as good job as Haaland did so far. When we consider all this, maybe they might be in search of a striker like Haaland this summer.
Dortmund lack of stable form to win Bundesliga. Sometimes, they score a lot of goals and has a long win run but sometimes they have issues with attacking and sometimes their defense are simply under performed. In general, they lose more points than Bayern Muchen in Bundesliga. Haaland is only a piece in their team and only Haaland can not cause to success or failure of Dortmund in the competition with Bayern Muchen.
Moukoko has a good growth for his career so far but I believe in future, when he gets mature more and has more ambition for his career as well as his price on transfer market is in hundred of million dollars, Dortmund will sell him as they did with their star players.
The problem is that the Barcelona can not afford Lewandowski, so they are backing down from recruiting the 33-year-old baller, while Thomas Muller has expressed hope that Robert Lewandowski still stay this summer, he said that he hopes that the man who has been his attacking partner for years to stay, Muller surely 1 of the players of Bayern Munich who expressed great lost if Lewandowski leaves the Team, but surely it is still Robert Lewandowski's Decision if he would leave of stay,
Barcelona can not afford to pay high salary for Lewandowski because their finance is not good.
They can not afford to give Lewandowski a tactic that he like and familiar with. They will give Lewandowski a striker position if he comes but tactic is different.
With Lewandowski, he receives lot of offers from big and rich clubs so Barcelona will not a first priority in Lewandowski's offer list.