Yeah Dortmund could have been even the strongest team in the Bundesliga and a huge threat in the Champions League every year as well. But they didn't keep nearly all of these players here.
The explanation for it is simple. This is their policy. They bring young talents, these players grow and then they get offers from bigger teams. Dortmund doesn't refrain from selling them by a big profit.
Some of them went because of a release clause though otherwise they could have made even bigger profits from those players (such as Haaland). Dortmund don't win titles much but they still make huge sum of money thanks to player sales.
To imagine that all these top players have played in Dortmund before they moved to their respective clubs now is to send much accolades to the club for its great efforts in sighting and acquiring young talents in their team. At a time, Arsenal was like this but looking at this big XI, for a club like Dortmund in the Bundesliga league to have groom such players, you've got to give them a lot of respect for that. Let's not forget to include the impact of Jurgen Klopp in the Liverpool after leaving Dortmund and how he had also groomed the Liverpool squad to face a tougher atmosphere for the subsequent seasons.
If this is an ideology that's adopted by the Dortmund management for now, I will really admire that courage to be able to figure out young talents that will make big names and also using that avenue to build their financial capacity. It's good to create an enabling environment for players to come and thrive and to also use that avenue to grow your finances especially if you don't have much to work with. It should not just be able to trophies all the time when the club is over stretched with financial crisis like seen in Barcelona recently.