This goes to show how incompetent Nagelsmann is he doesn't really care about the players and what they think, and what they are capable of doing, not all players will surely adapt that fast to all of his strategies especially those not as skillful as Robert Lewandowski, yes Sadio Mane has the talent but he can not do all of it, he needs to adjust slowly, and he just recently arrives at Bayern Munich so he has a lot of adjusting to do and he can not properly do that in a small period of time,
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.
If he can make Bayern win the Bundesliga last season,means he still is a good coach who just needs to change tactics from the present one he uses,if the one he uses currently is no longer working,he also needs to check what the problem really is and how to address it.One Quality of a good coach is the ability to change formation,tactics and method of play, if the former is becoming easy for your opponents to access.Changing tactics will enable them play in a way that the opponents will find it difficult to read.He should still be giving more time to change formations and see whether it would work for him or not.