Bayern is a very wealthy club with a very sound financial policy. Basically, they can keep any players they want. They also don't let players go easily. Lewandowsky did leave last season, but that must also have had to do with his age. They handled that reasonably well with Mane. And Sane has also come over for that from Manchester City. I don't know if they plan to get more players, but they already got de Ligt in the summer, which was also a good reinforcement. It doesn't matter who they play with, the B team is also so good that they easily become champions.
If Dortmund had adopted the style of Bayern Munich they would have been doing well and also be a rival to Bayern Munich. Bayern Munich don't easily let their good players go until they have a good player that can be a Replacement unlike Dortmund. Dortmund sells their players their important player's even without having a play that can be a Replacement. Bayern style of management is quite different from that of every other club that is why winning the Bundesliga league is easy for them unlike other teams.
It takes a long time and it takes a lot of money if you really want something like this to happen, we know that Dortmund always have some talented players but it's not enough because there has to be someone who is really experienced there and when it's wanted the higher ups always let the player go with big sales money so I personally don't really feel that something like adopting a style will be done because they must be aware that the risk of loss is quite a lot if they intend to compete even though at this time they are often said to be rivals.