Sadio Mane couldn't give quite the expected performance when he played as a centre-forward. And it is totally normal as well. Because he isn't naturally a centre-forward. Besides he has much more different characteristics than Lewandowski. The thing Bayern Munich need now is to sign a complete forward like Lewandowski. This can help them seriously about pulling themselves together.
Choupo-Moting tried to do some good things there but it wasn't enough unfortunately. Bayern Munich need a more reliable striker immediately. If Mane play as a left winger as well then their attacking line would be really strong.
I totally agree with you, I think Bayern's management is also very aware of this, they really need a single striker like Lewandowski and in fact Kane is a suitable candidate, but does Bayern not have other candidates who might have the potential to become the next Lewandowski, there must be a lot another, less exposed striker who could be a substitute for Lewandowski.