Regardless how good a player is, he can't do anything if he doesn't find a support from the other players in the team. CR7 did quite good in Juve and ManU but look how bad these teams were in these seasons although having good players. Many fans criticised the way CR7 is playing and blamed him for the way the team was performing.
Anyway it would be better for Bayern to find a younger talent. Having CR7 won't guarantee anything imo.
Ronaldo is a very good and reliable player, he puts in so much hard work to his game which has always shown in his performance in every game and has put him in spotlight through out his career but the success of a club does not depend on one player alone. It should be team effort, when one player is performing alone and others are keeping up low performance and low work rate it will also affect the team. Same scenario when Ronaldo played for Manchester United, he was putting in his best but the team was performing poorly and they couldn't get a good result at the end so it takes team work to achieve team goals not just individual effort alone.