Removing individual buffs...how would you replace them then? Because there are a lot of jobs that rely on their individual buffs to function. Melee and Tank especially due to the nature of providing damage in those individual buffs, with all Healers(except SGE) having some sort of damage buff or individual buff to provide either higher damage or faster casting. BRD has their own individual damage buff for Wanderer's Minuet. DNC has a ton of party buffs, but has to keep up Standard Step for itself to function. MCH...doesn't have any buffs for itself, and is probably the only exception here as Casters have their self-buffs to make them go faster or deal more damage at a given time.
To shorten it, basically if you remove individual buffs, then you upend entire job's functions and disrupt gameplay flow.
The last time I heard the word diversity was when Stormblood was current. After that all I heard was homogenization and fear-mongering of it. We have class diversity, but if we're going to talk about kit diversity, you need to determine what factors are required to achieve the level of diversity you're asking for - because I can imagine it's different between everyone here. Ask the question about your job as a SGE: "What makes my job stand out, and what is it missing?" Since I've played SGE myself the past tier, I know it's missing engagement, as are all healers. The solution to that is to provide more damage buttons to keep the player engaged while in healing downtime compared to actual downtime on the target - and it's something that the Battle Team needs to consider.
By looking at each individual job and determining its flaws, how it compares to other jobs, and also its critical issues for the role as a whole, you can find what is lacking in their 'diversity'.
In Heavensward the fear was struck in them about a whole role being locked out, along with certain jobs being locked out(MNK, Casters) in favor of higher damage. This was heavily prevalent after the 3rd part of Alexander was released and in Stormblood; moreso by a Piercing Debuff provided by DRG. It was the sole reason they got rid of Piercing/Slashing/Blunt Debuffs - to prevent jobs from being locked out. Yet, scroll over to Early Shadowbringers in P4S, and you find that double Caster has started to take over Ranged, except by a decent margin compared to it being buff-related. It wound up being damage related, which they've always fallen short on when balancing, so they implemented the 1% Buff per Role to incentivize they keep a static set of roles involved in all content as a band-aid for a problem that would be exacerbated in Endwalker for a singular Ranged - MCH. This drives us back to our main problem: The 2 Minute Buff Window.
In order to subvert this window, I do agree with what was said earlier: Critical Hit needs to be reduced in impact, as Critical Hit determines your Critical Rate and Critical Damage increase. This dual-use has made Critical Hit a monster since it became very prevalent in Stormblood, and once more exacerbated by the 2-min. Window for Critical Hit Variance.