Dortmund made a big mistake by letting such a player go. If they add some players like Arling Haaland to the team then the team will make a big impact in the Bundesliga next season. Because there are no special players in the Bayern Munich team.
Maybe you are the only one who thinks there are no special players in the Bayern Munich team, because maybe you don't really know the players in the Bayern Munich team. It's true that many of the players who used to come from Dortmund were good when they were in other teams so the price was also quite expensive because Dortmund did sell players with potential and didn't often sell players whose potential was still lacking. I also don't really understand the pace that Dortmund has taken in terms of selling and retaining their players.
Bayern Munich doesn't seem to have any special players, but from what I can see their squad is evenly distributed and also they rely on team play rather than individual play, so it makes them seem like they don't have any special players.
Borussia Dortmund always sells star players, many players have left for other teams just because they want to get big profits. Erling Haaland is one of the young players they have managed to create and now he is making it big at Manchester City.