I get the feeling that people think that things like piercing and slashing debuffs were just "neat little bonuses" when, in reality, not having them made the game outrageously more difficult. It wasn't a cool little job synergy thing, you were literally telling every tank except WAR to go fuck themselves if you didn't have slashing debuff, every phys ranged to go fuck themselves if you didn't have a DRG, and every caster to go fuck themselves if you didn't have Mage's Ballad. Stormblood was the low point of this game's job design in every imaginable way, outside of some rotations being a little more fun and involved. But outside of the stuff that activates the monkey brain neurons of the average casual, it was horribly unbalanced and a large portion of job mechanics that gave the illusion of variability just stopped existing the moment you got good.
It wasn't a skill floor or skill ceiling thing either. It was a skill "take one step up and suddenly you do 15% more DPS without actually having to work for it" ladder.