That might be true, but do you realize that Dortmund has now proven a couple of times that they can beat top teams? With some luck and on a perfect day I think they can beat Real Madrid. Just see how they managed to stop Mbappe from scoring two games in a row. I guess there is hardly a harder challenge than that. If they can stop Mbappe, they can also stop players like Vinicius Junior. And in a final I think everything is different anyway. Every player reaches new heights and there are so many small details that can be decisive. If Real Madrid doesn't score way too early in the game, then chances are good for Dortmund to achieve something great
When 2 teams go to the final it means they are the best team among the other teams and basically both teams are at the same level, the only difference is experience. Indeed, based on the squad, Real Madrid looks better, but there is no guarantee that Real Madrid will definitely win, the Europa League final is an example when a strong team like Leverkusen is defeated so the same thing could happen in the Champions League, right?
Experience might indeed be a big one here as Real Madrid is undoubtedly the most experienced team in that competition. And I think that this alone puts pressure on their opponents. Look how they eliminate teams like Manchester City or Bayern Munich or PSG. It often looks as if today the day has come where they get knocked out and yet again they can score out of nowhere. I never fully understood how that is even possible!
So yes, experience can make a difference. But the first point you made is also true. When two teams reach a final, it means that they must have been doing something right. They could get lucky once, but getting lucky all the time in a competition like that is impossible. And after all Dortmund hasn't only beaten teams like PSV, but teams like PSG and Atletico Madrid. Real Madrid is definitely not invulnerable. Look how close it was against RB Leipzig in the round of 16. Hell nobody was expecting that at all and Leipzig scored the equalizer away from home and had 20-11 shots! It was close to 50:50 ball possession. That's a good example where nobody thought it could go like that and Leipzig would have no chance at all.
I stand by my word that Dortmund should definitely not do some stupid mistake early in the game, like a dumb crossball at their own box or so. If they can play with highest concentration, this is going to be a great final for all football fans around the world. I am just sometimes a bit sceptical that Hummels will mess up a tackling and cause a penalty and in a worst case get a red card. That would be game over.