Kane doesn't have to go to Bayern for Bayern to be good, but they need some changes without a doubt. Mane could leave too, those two things are not the string that holds this team together. They can still not get Kane and send Mane away and win the title. All they have to do is find replacements and I feel like they are not really looking for that at the moment. They should be doing it as much as possible and it would end up with a good result eventually.
I personally believe that the best thing to do at this moment for them would be getting a pure striker, doesn't have to be Kane but it has to be at least a good striker, a Bayern level striker, if they can get that then the rest of the squad will do amazingly well eventually.
I agree with what you said, they need to get a pure striker, Bayern Munich actually has a squad that is not too bad. If they can find a pure striker who is hungry for goals then they can be good in the end, it doesn't have to be Kane right because there are still a lot of pure strikers out there who might be better than Kane, especially if they find a pure striker who is still young.