It's not about you playing FFXI. It's about the perception that you feel superior -because- you played FFXI.
And let's just straighten something out here: just because you keep moving the goalposts around and shifting your definition of "unique" to coarser and coarser grains, doesn't mean the classes aren't actually unique. Let's go over it again, from the top:
PLD/WAR: Differ in their styles. Paladins prepare with damage mitigation abilities, Warriors have some mitigation but also rely on having a much larger HP pool, a Bubble skill (Thrill of Battle), and a large number of Drain-type attack abilities. They are VERY different beasts.
SCH/WHM: Speaking as someone who plays both of these classes in endgame material they are -very- different, and in fact -because- of those differences, they have an almost glorious synergy. SCH have pitiful multi-target healing, their best skill being tied to their pet and only granting an effect equivalent to WHM Regen, but they have unparalleled single-target healing, incredibly powerful shielding (crit Adlo makes even WHM Stoneskin look weak), damage mitigation through Sacred Soil, and a lifesaving emergency heal button in the form of Lustrate. White Mages can do phenomenal burst healing and have one of the most powerful (and aggro-drawing) skills in the game in the form of DS+Medica II. Just one Medica II is enough to stave off even devastating raid-wide attacks like Titan's stomps and The Avatar's towers. They are different as night and day and it's -wonderful- that it is that way. You have one of them at 50, go grab your opposite number, hit up Coil or an EX Primal, and see what a difference it makes.
BRD: The only physical ranged DPS. Extreme mobility compared to SMN and even more so compared to BLM. Has excellent support utility even if a lot of players don't seem to know how to use it. Synergizes well with SMN/BLM due to their Foe Requiem skill.
SMN/BLM: One has huge flashy slow magic skill with terrifying burst damage and a very unique astral/umbral mechanic. The other one has a pet that does a pretty big portion of their damage, can serve as an extra tank in emergencies or to aid in specific fights (I've seen Mog EX run by using Titan-egi to hold the King while the two tanks grab a moogle each), and deal the vast majority of their damage through DoT spells.
DRG/MNK: I can't say a -ton- about dragoon, but monk is very, very different than any of the other three melee classes. GLA/MRD/LNC all focus around series of very specific chains attacks that when used in the proper order gain potency and various effects. But now look at monk. The specific order is actually irrelevant. Twin Snakes does the same thing whether you precede it with Arm of the Destroyer, Bootshine, or Dragon Kick. Instead, monk has three sets of three attacks each and move through those sets in a cycle, weaving together attacks as you go, on the fly. There's theoretically a "perfect rotation", but it exists only if you're hitting a training dummy (or Ramuh/T8 I guess). Every single attack you make is chosen from one of the next set in the cycle's three choices. Is my strength boost starting to fall off? Better pop in Twin Snakes. Is it -almost- going to fall off? I'll weave in one of my extra moves (Impulse, Fracture, Touch of Death, etc.) They even get an incredibly helpful healing buff in the form of Mantra. Dragoon has NOTHING like this, and to say otherwise is to take things so coarse-grained that you might as well claim XIV and XI are identical because they're both Final Fantasy-themed MMOs with classes based off of iconic clsses from the franchise's history.