Mechanics driven fights are fine as long as all the mechanics are fun and well executed and aren't just overconvoluted or thrown in droves for the sake of it, having reached T9 in Second Coil it sure is something figuring stuff out and executing it, but it isn't really that fun, it all just feels too mechanic. The closest comparison is a precision platformer like Super Meat Boy or I wanna be the guy, you have to time everything at the right moment and a small slip by you or someone else will probably mess it all up and make you go back to the very start of the level, as someone who 100% + whatever the extra % in SMB was, it's just as unfun as in there too.

Personally I really like Moogle EX because everything is mostly randomized and there isn't a strict order to things happening aside from phase changes, too bad people rarely do it because the rewards are just a neck accessory most people have by now.