Both Bayern and Dortmund massive disappointments. Is the German league really deteriorated that much in the last couple of years?
Less said about Schalke the better as well. Embarrassing.
Bayern's decline has more to do with Hoeneß, IMO. His squad management overall has been awful and he's really oldfashioned in his views. He's a little bit like Mourinho in a way. Wants to show the whole world that he can have success his, the old school, way. Great skepticism of the new generation of conceptual managers because they make things too complicated, doesn't rate tactical managers too much and so forth. He also likes to surround himself with yes sayers which is why he chose Kovac (one of "the Bayern family") and appointed an absolute fraud as a director of sports in Hasan Salihamidzic (also one of his peers). You need to see this guy live when he's giving interviews or press conferences. A puppet on a string without any insightful, innovative or even slightly competent views on football.
The weak league and especially the lack of a real competitor was a problem for Bayern ever since their CL win. They lacked a sparring partner and you've seen that when they faced top teams. Exemplarily last year when they were the far better team against Madrid but went out regardless because of silly mistakes, like a group of young and talented but inexperienced players. But now it is different, they aren't playing well, they are simply not that good anymore.
The league in general is actually on the right track, IMO. Dortmund has really improved again under Favre and I believe once they have a little more experience, they will be an exceptional team. Unfortunately for them they had their period of bad form when the going got tough in the CL so they sold themselves under value. We (Leverkusen) also look really good under Bosz and I have the feeling something is emerging here. Leipzig is establishing themselves at the top, too. Also, there are many very good managers around (especially Nagelsmann) and players that eventually will end up at top clubs.
IMO it will all depend on Bayern's behaviour. If they open themselves for new developments again and are willing to pay for foreign talent instead of trying to steal players from league competitors, the Bundesliga will get back to where it was 3-5 years ago. If not, they will suffocate the positive development many clubs are going through right now, especially Dortmund and Leverkusen. Then we are probably heading for a similarly depressive period as the early to mid 00s where no German team was even remotely close to the European giants at all.