Mobility alone is a huge benefit, because it provides many other sub benefits, and just lumping it into the word mobility massively understates what makes any-range/any-time gcds and skills valuable.
-Not having to alter play, or adapt/recover rotations due to mechanics,
-less needing to know the fight down to your specific skill speeds impacts, because heavy movement phases wont change your rotations or cancel skills.
-less impact on your rotation from other team members,
-ability to recover or adjust from failures without having to neglect or intentionally screw up your skill casts or rotations.
-Never having to risk danger by sneaking in positional
-Never having to hug tight, or worry about more specific over positioning to maintain GCD or other skill up-time. Good example of this is in E2 during chaos/retribution. Melees can maintain perfect up-time even during cycles, BUT it is massively more difficult to do so than as a ranged.
-Consequently to all of the above: less party adaptation is necessary, and your pDPS really can't be negatively effected by anyone elses actions unless they get you killed.
-Ability to suffer knockbacks without stressing about interruption. if you get the move off you get the move off.
-varied different raid events such as uplift in E4 require less foresight and planning than casters who can be interrupted.
Given ranged do have abilities that make some of these not apply, such as DNC for example needing to be in near melee range from time to time to perform perfectly.
But the point is No cast times+ No ranged restrictions + no positionals is an absolute and immediate massive decrease in the difficulty compared to other roles.
This being siad, I don't think the range penalty should be anywhere near as big as it is. All ranged (minus BLM) right now need a significant buff, TBH their DPS should only be minimally behind the rest of the cast.
I also am of the apparent minority that thinks difficulty should be part of the metrics defining balance even tho it is arbitrarily hard to compare with fairness. (particularly because skill gaps in logs aren't accurate depictions due to the varying nature of auto attack's contributions on different classes/roles) Yet this is already in essence why ranged dps tax is considered justifiable at all.
People defending the ranged tax need to realize that they are directly using difficulty to justify balance. I see too many people on these forums go: "Difficulty shouldn't be considered for balance, it is its own reward" then literally say a moment later "Ranged should be taxed because they have mobility" Its literally hypocritical.