In FF1 thru to FF6, there used to be several different types of status effects with several specific -na casts to cleanse them.
Esuna is a "cleans everything except uncleanable debuffs" which is honestly, silly.
But if there was 6 different debuff cleans, then every healer would need them, and would complain about the hotbar bloat for something that is barely used. Likewise Tanks and DPS would have no means of countering these except by potions, which means they would need to reserve six hotbar buttons for using pots. That is also, not viable.
At least in a MMORPG. And it feels like Yoshi-P doesn't really think much of status effect debuffs.
Realistically a healer should be doing all of the below:
1) Keeping all party members at full or near-full health (Cure 1, 2, 3, Medica, Medica II/III)
2) Physical Damage reduction (Protect), Mitigation of tank busters (Stoneskin) or magical damage (Shell)
3) Cleaning all debuffs (which last longer than the burst window) so you can't just ignore and heal through it.
Like the only dungeon in the game that actually used debuffs that way, doesn't even use Esuna to remove it. Aurum Vale. More debuff bleeds, or debuff stacks (120s) that can be cleaned please. Things like Curse, Disease, Debrave/Defaith, Freeze/Stop, Petrify/Numb, etc.
Then you have mini/frog/chicken/toy or something that makes the player just do 1's until cleaned.
Also "Reverse". Where it swaps Damage and Healing from the players party, so when that debuff is in effect, the healer has to stop healing or it will damage the party, and the DPS has to stop attacking or it will heal the enemy.
Esuna would need to be split into at least two buttons, one for cleaning debuffs that cause damage (what Esuna is for), and one for cleaning transforms(including mini and petrify), that stay transformed permanently until the dungeon is cleared if not cleaned.
These 15 second debuffs, can be ignored unless they are DOOM, and that's why some people don't have Esuna on the bar.