The last time Dortmund won the Bundesliga was in the 2011-2012 season and after that Dortmund no longer won titles in the Bundesliga including last season where Dortmund were only able to secure runner-up positions in the Bundesliga. Speaking of players, I see that Dortmund always have the best players in their squad who they will eventually sell to other teams for more money.
Because Dortmund is very good at training players and making players very talented as in several examples that have been seen by everyone, so Dortmund's defeat last season in the Bundesliga was not on the factor of their players, but on the factor of Dortmund's luck which was still very thin.
Admittedly, last season Dortmund's mentality could only reach runners-up in the Bundesliga, even though the title was right before their eyes, but they failed in the last match against Mainz. I agree with you, this is because many Dortmund players are sold just to get money and not a few Dortmund players are sold instead to opposing teams like Bayer Munchen. So do not be surprised if Bayer Munich's domination in the Bundesliga is difficult to be broken by other clubs, including Dortmund.
Whatever the drama of the Bundesliga, Bayern Munich is still the champion. This gives the impression that the Bundesliga is no longer attractive to overly dominating Munich. I hope that the Bundesliga will return to being competitive like the 2001-2012 period where there were several clubs like (Dortmund, Stuttgart, W. Bremen, and Wolfsburg) who were able to break Bayern Munich's dominance.