To be honest in this case Nagelsmann is still good enough for a coach but the scheme he plays is always the same and it is clear when he has met many times and has experienced this the other team will get a glimmer of hope because his scheme has been read and it has been proven in the last few matches.
If indeed he still wants to be at Bayern he obviously needs more effort in this regard because otherwise the word "failed coach" will be repeated and he will have to leave even before his contract expires.
He surely is a good coach, but if his play tactics don't work anymore then he surely needs to change it and let the team play at their own position that they are used to playing, you can not force Sadio Mane into a position that he is not very familiar with, it works on the 1st game, then why isn't working on the later games, I think Nagelsmann is questioning Sadio Mane this, but Sadio Mane has a tendency that he of making mistakes when he is not very familiar with his plays,
As far as I'm concerned, Nagelsmann was not accused of being a bad coach while Robert Lewandowski was a member of the team. After Lewandowski left the club, this rumor of him being sacked only grew stronger and stronger. There seems to be a connection to be made here, so I think we are on the right track.
It is indisputably true that Lewandowski was their best player and their main scoring machine, and he was the man behind it all. The fact that he has left, even though Bayern has bought Mane, does not make him a lethal striker like Lewa was. As a result, I think changing the coach would not mean anything if they are not able to sign a striker who is effective.