I don't think it is all about adaptation, but about the quality and balance of the Bayern Munich squad. A lot of people have been saying that this is the best team they ever had, but I never understood why they are saying that. What about the team when Ribery and Robben played on the wings, Lewandwoski in the center, Neuer was in his prime and Lahm also was still playing? Was that team any worse? Definitely not in my opinion and all those players have been pretty reliable if they were healthy. Robben was injured too often, but when he played he was always dangerous. Sané will never replace Robben. Gnabry will never replace Ribery and no defender will ever replace Lahm.
Tuchel overestimates the quality of that team. If they don't add some high quality players, they will have problems again next season.
I'm not going to try to compare with their squad when some of the players you mentioned are still in their squad. However, in my opinion, comparing between the squad before and now, of course, we will always find differences, whether in the way they play or the coach's strategy implemented, because their coach is also not the same as when the players were at Bayren Munich.
The coach's assessment will also differ from their point of view, so it's only natural that their opinion will differ from our opinion of their squad.
I see what you are saying but the statistics also speak for themselves. You could also take the squad from 2013 as an example when Bayern played a record Bundesliga season with 98:18 goals scored and won the Champions League and there was almost not a single game where Bayern made mistakes. It was absolutely superb and therefore it doesn't make sense to now talk about the strongest squad ever. In the end success is what counts. I am not someone who disregards performance when there are no trophies, that can happen. Sané is a good example. Everyone says he is one of the best in the world. Perhaps in 20% of the games he plays, does that make a player one of the best in the world? Would Guardiola let one of the best players in the world easily go?
We'll see how they are going to do next season. If it is the same as this season, it would be a good proof that this squad is certainly not the best. I already doubt it but maybe some have their reasons to believe that.