If you are raising a player who is showing good potential and eventually when he becomes one of the world's best, you sell him to your biggest rival, Bayern Munich, you are not going to have much of an accomplishment to talk about. That’s exactly what has been happening with Dortmund. There is a reason why they generally cannot attract good players, and even if they have a good player in the team, he wants to leave when he is approached by other clubs.
They still enjoy business in the players they have so that competition for the title race is only limited to hopes and targets that are difficult for them to achieve. How many players who have quality at Dortmund end up being sold and generally they are successful at the club and Haaland is perhaps one of the closest examples at this point. If Dortmund still expect profit from selling the players they have and still think this is a profitable business and don't change the club vision, so whenever they will find it difficult to become a club that can compete at any level.
Furthermore, I also see that Dortmund has no desire to recruit quality players, they prefer to find and find talented players and then make them have a large bargaining value and sell them to other clubs, for me this is still a big problem for Dortmund.
They are not going to improve as a club and not going to be a desirable destination for great players if they do not change their approach. And I understand that in the end, a club has to think about money.
But the problem with Dortmund is that they are only thinking about money. And they are not going to do very well with that mentality. It would have been good to even see if they actually invested that money into making a really good squad. But they don’t do that as well. The sad part is that they know this very well, but they do not want to do anything about it. They just want to keep doing what they are doing.