-snip-
Even though Bayern Munich have lost their main goalkeeper who has been on the crossbar for many years, but I believe it is not a big problem for them in this Bundesliga. As you said, Bayern Munich has no competitors that will make them have to work twice as hard for the title. Borussia Dortmund, which has been their main competitor, is now in an unfavorable situation for Borussia Dortmund.
Indeed, Even though we know that Bayern lost their main striker when Lewandowski left Bayern, in fact, they are still a solid and strong team. Moreover, there are no rivals in the Bundesliga so it won't be a big problem for the team. But that doesn't mean they don't need great players in their positions because they are not only struggling in the Bundesliga but also in the Champions League which is very tight and difficult to compete in.
Maybe Dortmund aren't in a very favourable condition in the league now. But even if they were at the second position in the standings they wouldn't still have been able to compete with Bayern Munich at the same level.
Dortmund's ability, especially this season, has greatly decreased. Especially in the last few matches. Even today, their position is only ranked 6th in the Bundesliga. They are not as competitive as they used to be a little bit able to rival Bayern, at the moment, they are not.