I'm curious, is it only me or the Infinite Castle got a lot easier after Floor 80 ? And I think 100 was as tough as 80, but further levels were pretty smooth sailing for me. But I'm so glad I cleared floor 80 and then climbed up to 130 for the good 6* FM (my goal and unexpectedly I somehow climbed from 80 to 130 in one go)
From my experience in the game I used to play, the devs actually did something like this too, they tuned newer contents easier than old contents. But I expect higher floors will require something really OP like Corbett or Pavonia + Adlay to clear, but not now I guess. Honestly I really like this mode.