Then I have to disagree strongly with you. There are some things that are just obviously more skillful to do vs. other things. Saying it's subjective is an hollow observation. Yes, everyone is skilled differently at the game to some extent, and some people are more gifted at doing things most people find very tedious than others, and to that, they will be advantaged in life by it. Life isn't fair, some people's experiences/genetics are going to make them succeed better at certain difficult things. That doesn't mean you discard the importance of taking in consideration the difficulty a class possesses when determining balance.
Requiring say one class to do 20 extra button presses with very unforgiving restrictions on half of them compared to another of the same role and balancing them around only ever being played at 100% optimization is not balanced at all. You can't just make a class clearly more tedious and complicated and vulnerable to error, especially under pressure, and not consider their balance vs. a class which has extremely less to do with less restrictions to have optimal output. The argument of subjectivity in difficulty only goes so far when you are talking about how many actual buttons and restrictions a player has to play around vs. another. It's illogical to suggest that a class that has more red tape to get over and more buttons to sequence in perfect execution without dying to end game mechanics is of negligible difference to one that doesn't. That there is someone out there who can potentially do all those things without error most of the time doesn't change that. Good for that person, they deserve to do a bit better by taking on a more challenging class regardless if it's due to innate abilities or not. Even among the skilled though, humans aren't computers, sometimes they just make honest mistakes, and classes with more to do are by nature more prone to such human errors, however seldom.
So, yeah, if you just aren't as good at the game but want to still do all the content in the game, there should be classes that trade a bit of ceiling for a much higher intermediate floor in what they have to offer in performance. Or, perhaps you just want the consistency of a less complicated class. It's a fairly common preference.
Bottomline though, demand vs. performance ratios vs. ceilings vs. floors are valid considerations in class balance for ffxiv. Lower demand high performance kits are going to be more appealing than high demand, higher performance kits for most people in heavy mechanic fights or just casual players. Even for very skilled players, maybe you want to trade the potential to do 3% or so extra dmg over your rivals to just make sure you experience less potential wipes with a particular group via a less complicated class. Such options existing is a good thing for the game in my opinion.