Bayern Munich and Dortmund battle it out every season in the Bundesliga, Dortmund unfortunately lost last season. However, I think if the Dortmund team adds a suitable player to replace Haaland, then Dortmund will go ahead of Bayern Munich.
So by your logic Dortmund should have won the league when they had Halland.
Even if Dortmund get a Halland they will still not be able to win the league because other part of their squad needs strengthening. The Dortmund team may have good players, but to say the truth they don't have the quality of players Bayern Munich has. Also, Bayern has more quality on the bench. Dortmund lack quality squad depth. Sadly, they don't have the funds to keep a big squad unlike Bayern Munich.
This was way I was very disappointed with Dortmund when they failed to win the league last season. That was a once in a while opportunity and they blew it. They had all the took to win that league but they fumbled till it got to the last game and they still went ahead and got only a point in a match they could easily have won at home and won the league. Till this day I still wonder why Bellingham didn't start that game.