Well, first, I would argue that well over 90% of FFXIV's lore and story arcs *are* original. The main scenario, give or take a minor shout-out, is entirely its own thing, for starters - the events, location, characters, and even the application of the references to past series that do exist are XIV Exclusives. The world of Hydaelyn itself is completely original as well (and, I would argue, the most fleshed-out world in the franchise - though I'm sure some would debate that).

Now, the game is also a Final Fantasy Theme Park by design - Yoshida himself has used these exact words. As such, there are indeed a number of storylines that reference past games more directly, alongside the other minor callbacks and references sprinkled in. The thing is, I'm not sure they're as common as some would imply. ARR had Crystal Tower, sure, but that was written in such a way that tied it inextricably to the world and history of XIV. Meanwhile, I can't think of anything that's a comparably-large reference in Heavensward.

Looking at Stormblood: Omega does certainly reference FFV quite heavily, and though it's once again entirely in the context of XIV's world, Exdeath gave me a bit of pause. Though he, like the other bosses, is discussed as if he's a legendary figure in Hydaelyn, little other context or buildup is given, making the excuse for the reference feel a bit cheaper than usual. However, I'm willing to see where this goes; one (very minor) slip-up isn't enough for me to write off the dev team as having succumbed to Crossover Fever. And as for Return to Ivalice, let's wait for that to drop before we call creative bankruptcy. If it ends up being like Crystal Tower, I think it'll be fine; if we cross a portal into the world of Tactics and XII, I'll be willing to concede the point.