We don't need more customization in our classes as much as we simply need more dynamics added to them and quality of life overall. And what I mean by that is to strip some of the rigidity in the current rotations away to make them more flexible. Some good examples of this are the slow, long combos of Dragoon needing more breakpoints, the positionals and stances of Monk needing more flexibility and the sheer lack of interaction between the disparate parts of their kit needing to be addressed, the Heat generation and Wildfire/Overheat mechanics alongside all the unnecessary feeling buttons in Machinist's kit gating it from the majority of players simply because of how much of a clunky mess it is, and the aetherflow lockouts on Summoner that forced it to be a phase based class instead of building on the rotation players adopted in Heavensward that inherently had more flexibility. These need to be altered (or in the case of Summoner, removed) to be more accommodating, but still matter.

BLM and SAM are probably the most balanced in this regard. BLM has more than enough cooldowns to help with their turret gameplay, and really only needs one tweak to make Thundercloud more appealing to use during their Astral Fire period, while SAM could see the positionals on their weaponskills removed in exchange for generating more Kenki if a weaponskill got a direct hit or something similar and not suffer whatsoever for it.

The tanks and healers also need to evolve, but that requires SE's raid design to evolve with it. They need to take more risks again, and reflect how players actually play their game and the meta perception that creates, not how their isolated testing goes.