Have I unlocked all the game mechanics?

[Morelyn]

At level 27, I've done several of the first dungeons and have unlocked city travel, retainers, grand companies and have gotten my chocobo.

My question is this: are there any further game mechanics (i.e., not including dungeons, primals, etc.) that I have yet to unlock through doing the story quests? In other words, if I never did another story quest, what would I be missing other than more dungeons, etc.?

[HEC]

Skipping the main story quests will exclude you from accessing majority of the dungeons and trials. There is also lvl30 side quest which unlocks the chocobo's companion capaility. Skipping higher level dungeons and trials will result in very boring leveling experience as well. Just out of curiosity - what exactly are you planing to do in the game leaving the main story aside?

[Naria]

Assuming you mean all story quests, if you don't do continue through the story quests you will be unable to access jobs and the associated abilities, certain general abilities for treasure hunting and desythesis, glamours, chocobo training, the beastman vendors, the sightseeing log, some emotes, possibly PVP, as well as most of the content of the game. Also there is a fair chance that if you raise a class to 50 with no job you will get mistaken for a RMT by the community, at they tend to be the only ones who completely abandon the story quests, as opposed to just progressing slowly.

[Enkidoh]

As HEC and Naria have mentioned, progression in the storyline will continuously unlock new content as you go along, even after completing the 'main' storyline - you cannot get your relic weapon without finishing the main story for instance. Also reaching a certain point in the story is required to allow access to the Isles of Umbra, which is necessary for the final part of the Hunting Log. And there is much else besides that is also unlocked by storyline progression. So yes, you need to undertake the story in order to access everything the game has to offer.

[Eltaire]

Some of the later high level (post level 50) content requires that you have completed the story to unlock, so it's recommended to do all the main scenario quests to enable you to continue with, and unlock "Chronicles of a New Era" quests which are actually quite fun.

[Garlyle]

Some of the later high level (post level 50) content requires that you have completed the story to unlock, so it's recommended to do all the main scenario quests to enable you to continue with, and unlock "Chronicles of a New Era" quests which are actually quite fun.

Basically everything that's "level 50" content requires the completion of the Main Story, actually - I think Wanderer's Palace might be the only thing level 50 content that doesn't require completion of the 'final dungeon' that is Praetorium.

As mentioned, there are lots of mechanics you've still yet to unlock, some of which will also be tied behind story progression.

[Kloe]

As some people have said to describe FFXIV, the game doesn't start until you're lvl 50 and have completed the 2.0 main story quests. Obviously there are things you can do without being lvl 50 and not having the main story quests done, but you're severely limiting yourself in what you can do and will most likely get bored with the game and quit eventually.

[Niwashi]

Assuming you mean all story quests, if you don't do continue through the story quests you will be unable to access jobs and the associated abilities, certain general abilities for treasure hunting and desythesis, glamours, chocobo training, the beastman vendors, the sightseeing log, some emotes, possibly PVP, as well as most of the content of the game.

No, most of that is just level dependent.

The Summoner job is an exception, as that one requires having beaten primals during the main story, but the OP is already far enough in the main story to unlock Summoner since its level 30 quest only relies on the level 20 Ifrit. (Its level 35 quest, however, requires having beaten the level 34 Titan, so by then you need to be pretty well caught up on story quests.) Neither Scholar nor Bard jobs have any such storyline progression requirements. (I'm not certain of others, since those three are the only ones I've unlocked so far, but I think most of them are like Scholar and Bard, where you only need the appropriate levels.)

Nor do treasure hunting, desythesis, chocobo training, sightseeing log, or PVP require anything in the main story beyond the point where you join a Grand Company. (I'm not certain on glamours or the beastman vendors.)

By the time you join a Grand Company, you have all the features the main storyline will grant you up until endgame. (At endgame, though, as several people have mentioned, pretty much all the additional content and questlines require having finished the main story.)