This is what is not liked about the Bundesliga, every time there is a good player from another team, Bayern Munich always targets and buys him. That's why it is difficult for Dortmund to win the Bundesliga because all their players were sold to their rivals. This will also happen to Leverkusen next season, especially now that Leverkusen players are starting to be targeted by European teams and there are even rumors circulating that Xabi Alanso is also being targeted by Bayern Munich to replace Tuchel at the end of the season. So it can be predicted that Leverkusen next season will not be as strong as now. I'm not sure that next season Leverkusen will be able to compete again for the Bundesliga trophy.
Why do you feel that it is not like or that there is something wrong when Bayern Munich with its money power recruits anyone they like?
Actually, the problem does not lie with Bayern Munich, but because even so far without being asked Dortmund will still sell their star players to other clubs, because indeed they get a big profit when selling these players and maybe only Bayern Munich really dare to pay a high price for these players, I think to be a club that wants to compete in domestic and European championships Dortmund should no longer sell their star players.
About leverkusen, I quite agree with your view, it is difficult for Leverkusen to keep their best players next season when they get offers from big clubs, especially reportedly Alonso will also leave for Munich next season, so automatically Munich will also recruit some reliable players Leverkusen to make their squad even better next season, and as you said of course Leverkusen will return to being a mediocre club next season if They lost Alonso and their best player.