If Dortmund's luck is with them, they can beat Real Madrid and qualify for the title, but performance-wise, they can never beat Real Madrid.
Dortmund have to prepare well in tactics with multiple tactics for possible changes in the final match, then when they go to play the final, they have to fight seriously for chance to win the match. Luck is important but it won't come if Dortmund won't seriously play to defend their goalkeeper and to find winning goal.
If we compare with a strong and experienced team like Madrid, Dortmund is a mediocre team. In terms of experience and squad, there is no doubt that Madrid will have the upper hand. But the Dortmund team is in good form now. This team was very tactical against PSG. And Dortmund's defense is strong enough. This is why there is no chance of underestimating the Dortmund team.
Moreover, the Champions League platform is always very competitive. Underdog teams often win against big teams. So while Real Madrid are in a strong position, I wouldn't say they are in a very safe zone. Defeating Dortmund is indeed difficult for Madrid now. And the final match will be very competitive. But I don't think we will see too many goals. I think both teams will play in defensive strategy.