If we compared between Bellingham and Sabitzer skill i think Bellingham is slightly better but indeed after Bellingham leave this team Dortmund was attempts to look for his replacement and this summer so far Dortmund has been bought 2 midfielder players Sabitzer and Felix Nmecha from Wolfsburg and for Nmecha this player has impressive performance with Wolfsburg that as a young player he can able to being an Wolfsburg key player and it proven from his statistics that during last season Nmecha was played 30 times and scores 3 goals in Bundesliga and he has help Wolfsburg to finish at 8th place and between these players i think Nmecha had a potention to being an the replacement of Bellingham instead of Sabitzer
I agree that Sabitzer will make sure that they are not getting that much worse suddenly, plus he was a lot cheaper so they made some money from that. We are talking about getting a player from Bayern, that's always a good indication that the player will be fine, plus he will be physical fit for sure, they focus on that a lot.
Considering they have spent about 50 million for the midfields, and made a total of 100 million just from Jude, they still have nearly 60 million euro that they haven't spent. They may or may not spend it, but they should if they want to win the league already, just get one player for 60, that would be a great player if you do not overpay for someone, they could get a huge name and that player can help them get it.