If cbu3 doesn't want harder content then how about removing the scripted fights?
The solution is simple, remove the script and let boss encounters do mechanics randomly.

An example of this would be Amon (should be Amen, but I'll forgive them since they're eurocentric) in Crystal Tower. Instead of:

auto attacks
2. Circles on the ground
auto attacks
3. Line lazer
auto attacks
4. Meteor towers
auto attacks
5. Stand on circles

Rinse and repeat

It would be:

auto attacks
2. Rng script: Stand on circles
auto attacks
3. Rng script (can't use stand on circle): Meteor towers
auto attacks
4. Rng script (can't use stand on circles nor meteor towers): Circles were 10 people stand on them
auto attacks
5. Rng script (can't use circles, meteor showers, nor stand on circles): Use line lazer

Now all of a sudden a Crystal Tower run you did today is different from the one you do tomorrow.

This way you kinda keep the same difficulty but you keep the user (player) engaged in the fight as they don't know what will happen next during the fight. Currently the game's extremely predicted, to the point where a preteen could learn the scripted fight and rarely ever take damage. That's the level of engagement of this game.