one day I imagine when Dortmund did not sell these talented players and kept Haaland and Bellingham Im sure Dortmund not go down like this and also winning the bundesliga title a bit easier to break the record but after all this has become a habit dortmund when getting young players built for getting new talent then selling him over Dortmund does not need reliable player and not want a title in bundesliga. It is very sad to see dortmund performance lately which has appeared very bad and whether it is successful this season will be able to build talented young players again but what is certain is a little sad to see bad things happen to Dortmund.
You're right though cause I could imagine what their team would had looked like with Haaland and Bellingham still involved in it, even though they didn't win the Champions League, they would've probably won the league title and be very invisible, but consider Dortmund a more business minded team, because they careless about winning trophies and are more focused on buying youngsters across Europe, develop them into future prospects and sell them for huge fee to top clubs when they're fully developed, just like I happened with Sancho, Haaland, Bellingham etc.
So far they haven't been in their best form and are still struggling to win matches, their performance is not all bad because they're still unbeaten just that they lack the ability to score against their opponents which has made them to draw their last two matches, they still have young talented players in their team and hopefully for them Karim Adeyemi would be the player they'll cash in on next summer.