If only they had reduced the number of sales of their quality players and kept more within the club to achieve, I'm sure they would have achieved something impressive by now and maybe they could have won the Champions League for the second time. But that's them, business is business, if there is a player who has the potential to bring in a lot of money they will not hesitate to let him go, even if that player is a very scary specter and has contributed a lot to them while in the squad.
And yes that's Drotmund with all its business. Lol
For Dortmund in a season not selling one or more talented players is like feeling that something is missing and they will do that continuously. It has become a tradition for Dortmund to release talented players and it is not surprising that in the end they have only been a business club for more than a decade. It seems that Dortmund's owner doesn't mind this either and what is important is how this team can survive in the competition with stable finances. I think we will still see this tradition for a very long time and again for them the title is not that important as long as they can make a lot of money from selling their players.
We can't complain about this in Dortmund because that's how their business works in Dortmund and that's how they make money. Dortmund usually invests in younger talents and grows these players after a few seasons they will sell these players to other top teams for much more money, however, I think there are many other players who were playing for Dortmund and then Bayern Munich bought them for more money.