You do make a good point, the majority of ex Dortmund players who left in recent years have really struggled big time to reproduce the same kinda form. Even Lewandowski is a bit shit in the CL. Sancho seems like a proper player with reliable technique as opposed to Dembele, that doesn't guarantee anything.
Personally I'd avoid Dortmund players
This is such a stupid myth. Clearly Lewandowski has established himself as one of the best strikers of the past decade, and with 53 CL goals he's the 6th most prolific CL goalscorer of all time despite playing only 80 gamed as opposed to those above him.
Hummels was one of the best CBs in the world for a few years.
Also Gundogan is playing at the level that was expected. Including his injury issues he's had at Dortmund too.
Aubameyang was available for 50M the year we and Chelsea were fighting for Morata and Lukaku and heavily overpaying. In hindsight I suppose everyone would agree Aubameyang would've been better. If anything this shows the two Spanish giants get to sell their dead wood for far too much once again.
Mkhytaryan was shit at Dortmund for two years before he showed any skill, which only worked in a very specific Tuchel system, after which we bought him and he turned shit again. Simply a bad buy by us.
Then there's Dembele, clearly one of the most talented attacking players around, but he's had mental issues also at Dortmund. His behaviour was bad and the manner in which he forced his move, shows his character issues. Barcelona was warned beforehand.
The only one that genuinely surprised me is Gotze, but then I found out he had a metabolism illness from which he never did and never will fully recover.
As far as I can remember, those are the only sales they made above 20M. The verdict is still out on Pulisic.