It will be difficult for any team to play against Frankfurt because they are in excellent form, had plenty of time to prepare, and have kept their key players. Bayer sold several important players, and then made a few transfers, but those were done under Ten Hag, and the new coach may evaluate these actions differently. Of course, the players will try hard and may even play better knowing that Ten Hag is gone, but Frankfurt is not an easy opponent, even though Bayer beat them twice last season.
You just generalized it when you said it will be difficult for any team to play against Frankfurt because they are in excellent form. There are lots of teams in the Bundesliga that can rip apart this Frankfurt team when they meet even with this form you say they are. I'm not even going to add Bayern Munich to list of teams that will do the job because we already know how it's going to be for both of them.