Why refusing customization is a fallacy

[Parawill]

The only actual customization in this game is through the illusion of materia melding (Zodiac Weapon and crafted gear), glamour and party composition. You have your pseudo-customization with your cross-class skills, but most jobs ignore the few skills they get because they're beyond useless (Physick & Ruin in White Mage is dumb).

Adding in the suggested customization would be completely foreign to this system, especially since party composition is the only real customization in this game. While it would be fun to specialize in a certain elements as a Black Mage, taking a glance at other games and classes you come to realize that not only would Square Enix have to completely redesign all classes and implement an entire new system to do this, they would also have to create so many new skills and different playstyles per class that you'd being to wonder why they're changing how FFXIV works and not just make a FFXVI. And besides, what would an Ice Mage do over a Fire Mage? Slows? Vulnerability? How about Thunder Mages? Stuns? Silences? While these myriad of debuffs may seem fun, you can already tell which classes will be preferred over the other, considering ailments aside from damage reduction (Storm's Path, Virus, Disable,etc.), vulnerability debuffs (Trick Attack, Foe's Requiem) will be preferred over others as most other debuffs are either useless in most situations.

In addition to this, you'd have to recreate encounters (Primals, Coil, Alex.) to accommodate Yoshi P's vision have making every class viable for all content. What this idea is suggesting not only backtracks the game itself but requires more effort than I believe some can comprehend.

On a side note, just because you can doesn't mean you should.
(Ignore text in picture. Refer to being able to put 6 Magikarps in your party).