Of course, friendly matches will never tell the whole truth about what awaits us in the regular season. However, I think it will not be easy for Bayern to fill the gap that arose after the leaving of Robert Lewandowski. In today's game against Manchester City you could see the difference. Hopefully Sane will soon begin to get understand better with the other players in the club and the team play will look better, but if they don't raise the level then Dortmund may finally have a chance to fight for the Bundesliga title.
I agree with you because most of the time these friendlies are having not serious impact on teams and players performance as these are just for preparation for them in season, and they have to do some strategies and working on different systems for their teams.
With this all most chances they will improve and having better results in next matches because now they are going to live without star player and having big challenge here they have some better news as their most competitive challenger Borussia Dortmund is also lost their main striker due to injury, and he is coming back after two or three months which can give them some good edge, and they can do much better than fans feelings about them in coming season.