I realized the main reason why Kaiten is getting removed is because of "button bloat"
You know what kind of button bloat I'd like for the to remove. Make High Fire II / High Blizzard II an upgrade of Fire III / Blizzard III. I never quite understood why we have different spells to swap Astral and Umbral phases for single target and AoE.
Black Mages have shiny new spells they never use in raid. Not to mention the slight change to Ninja. Making Mug the new Trick Attack is an obvious way to lower skill ceiling because they don't want Genins to lose their party buff because they bunnied. Genins will still be underperforming because they'll bunny a Ninjutsu anyways.
Personally, it started with Healers to lower their skill ceiling to DPS. Monk/Summoner followed (Monk was done much better than Summoner). Summoner became a complete joke in the raiding scene. Painted as a physical DPS that deserves to do no damage for being a no brain job.
If you guys really want Kaiten back for the uniqueness and gameplay, do look back a bit and support the jobs that got butchered. Summoner is super popular now, clearly a "success" but people still play it bad. Summoner is clunky, Carbuncle is 1 button from being glamour and... let's be real, some Summoners will never use Radiant Aegis in their life so it is already glamour for them.
How about Dragoons that lost their aura in the name of simplicity? Or Monk losing their aura from GL. These may as well be called just flavor and glamour but it does remove identity to the job imho.