Life is not reverting back and use many assumptions like this. Dortmund succeed with their strategy to build up their team with young players around the world, then sell them with high transfer prices and repeat the cycle. They did not win many titles recent years but maintained their position good enough in Bundesliga and Champions League.
It means Dortmund are growing up sustainably and I believe they will continue with this development strategy than taking more risk to buy star players and pay them higher salary. A healthy finance from sustainable strategy is key of a club future and Dortmund are doing it well.
It's clearly regretful to revert time and look at star players they sold recent years but you can not achieve all things in life, only one or another.
The issue is that if they didn't sell their stars then they would have a great eleven and yeah that's awesome and all that. BUT! the point here is that they had so many stars in their team, and looking at how much money they made from selling these players, and I am looking at just the last five years, and they are in profit, and where is all of that money? They are not spending it back, this team is like running as if it was a company, trying to make a profit.
That's not how it works, teams spend more on transfers than they get, because they also have other income like tv rights and merchandise and tickets etc etc. It means that they should be able to actually make some profit from other stuff that they put on top of their sales and that's what they spend on transfers.
Dortmund isn't like that, their income from transfers is higher than their spending and that makes no sense to me, look at how many amazing players they had in their history, many of them gone just recently, hell Jude himself is just 100 million, and yet when you look at what they did with that money, it is nowhere to be found. What are they doing with all of that money if they are not spending that money on buying up players?