how on earth is anything challenging to execute without having to learn anything new to actually make it a challenge? Especially in a game like this?

This isn't an action game, and they can't just make AoEs detonate faster or throw more of them at the screen, that's a faker difficulty than one that makes you fight blind.

And TBH, there aren't TOO many fights in this game where the mechanics just come out of absolutely nowhere. There are some like t5 or t9 that are unforgiving to learn, but most of them are lightly touched upon in the HM fight before they blow up in your face in EX.