Aesthetic or gameplay?
PLD: Holy knight/guardian. Party utility (Clemency, 2x raid defensives, Cover) to protect your friends, semi-caster phase, holy magic sprinkled between swordplay. And BIG swordplay...which is magical.
WAR: Berserker guardian, "Too angry to die". LOTS of self sustain and big damage burst.
DRK: Dark and broody, chaotic good sense of justice. SHOULD have lots of drains and stuff but doesn't; instead has busy burst phase and simple maintenance phase.
GNB: Bodyguard with a sword that goes pew pew; Whatever... Good balance of offense and defense, faster paced more like a melee DPS with CD management.
WHM: Healer without parallel. Big heals, should probably be more MP efficient; should also have defensive buffs but doesn't. Instead it has big attack spells (that aren't named Holy, oddly) for some reason.
SCH: Healing team with your Faerie partner. Weaker heals but mitigation to make them spread further, can have Eos act independent of your position; has some neat setup/combo actions (Recitation+Adlo+Deploy)
AST: Twister of fate. Lots of party buffs, busy burst, pretty animations.
SGE: Techno-mage Greek doctor. SHOULD be setup and payoff healer, or like GNB where it's the healer for DPS mains. Instead it's a SCH with less clunk? Smooth as butter and well liked, though. Lots of oGCD weaving heals.
MNK: Hard hitting, fast attacking brawler. Positionals, a long combo that feels free flowing while not being so (captures the feel, though), bit janky with the Nadis, super high skill ceiling. Fastest GCD (GL).
DRG: Consistent pressure attacker. Methodical rotation "on rails", very rigid but satisfying, lots of jumping animations.
NIN: Stealthy, quick, agile fighter from the shadows. ...the most flash animations in the game for some reason. Burst is super hectic, GCD is fast (Houton), button bloat and jank though, downtime is chill, Ninki seems...pointless and annoying.
SAM: Skilled blademaster. Several interlocking combos, and Iajutsu is kind of fun to charge then unleash. Easy to get the hang of but hard to master to the highest level.
RPR: Pact with the Void for bursts of power. Largely fulfills the fantasy with a pretty simple rotation, few positionals, snappy and hard hitting burst phase. Not for people who don't like pacts with Void/darkness/evil creatures trying to eat your soul.
BRD: Supportive team player with party buffs. ...the buffs are three, and you rotate through them rigidly. Kinda sucks. Also you have DoTs for some reason still, and random oGCDs on the side to juggle for...reasons.
MCH: Steampunk gunplay with fun gadgets. Simple base rotation but with plenty to mix it up, high intensity burst phase, does decent damage now and has some party utility. Has a shotgun. A GD shotgun. For AOE, but it's still a shotgun. Chuck-chuck!
DNC: Supportive team player with party buffs. Robbed SB BRD and stole its utility. Boost your party, super-boost one person in the party. Relatively simple rotation that is never the same twice due to procs.
BLM: Master of destructive magics. Largely fulfills the fantasy having big damage and slow cast time spells that feel powerful, but very mixed Job depending on whether you like the encounter mastery you need to know where to stand and play it well.
SMN: Master of powerful summon magics. Largely fulfills the fantasy having big summons and flinging them at the enemy left and right. Some people hate its simplicity, others love it. Most played and probably the one non-DPS players like the most. Can Raise.
RDM: Jack of all trades, master of none. It has a decent heal it mostly doesn't use and can't really do much healing, making it less "jack of all" and more "master of middling DPS"; rotation is simple to learn but hard to master, has Flare and Holy for some reason, but doesn't learn Cure until late, though it has a couple party buffs. Melees more now than it used to, but doesn't feel like a melee, despite RDM history saying it should ("jack of all...", not so much). Res Mage.
BLU: Master myriad magics from beasts and monsters, tailor your versatile kit to deal with any situation. DOES meet that fantasy...but can't do end-game content and is limited out of other stuff like Deep Dungeons, etc.