You have said it all, Luck is what is always on Madrid side. In the group stage, they will struggle to survive and after qualifying to the round of 16, they will start playing in their best performance joined with luck, gives them a upper hand over every other club in UCL. I am expecting to see them in the finals, because it's certain that they will be in the semifinals.
No, you can never win a title with luck. You can win a match with luck, but you can't win a match with luck. In the end, Real Madrid won the match based on their experience. They have the ability to handle the pressure of big matches and they can play great football under pressure in a way that other teams can't. You can call Real Madrid's win against Atletico Madrid based on luck, but I would prefer to call it experience. Real Madrid was lucky in that match but luck was not the main reason for the win. In the trybreaker, Real Madrid used their experience and appealed for Alvarez's goal to be disallowed, where they succeeded. This single goal was the main reason for changing the outcome of the match.