In other words, it's the least original game in the Final Fantasy mainline. FF has really been ups its own ass lately within its spin-offs, which have turned from mostly original concepts to fanservice crossovers, but it's a shame that even a mainline game is like that now, even though it started off pretty unique aesthetic/lore wise. (That plus shamelessly asset recycling from FFX, FFXI, FFXII, FFXIII, and even Dissidia, despite all of those games having their own art design).
Just because FFXIV is a giant love-letter to the series hardly means it's not original. If anything, FFXIV is holding a monopoly on their best storytellers right now with exquisite, character-driven content updates. It borrows, yes, but every Final Fantasy game borrows to an extent from the previous ones.
FFXIV is crammed full of amazing original content, and many of its original characters, races, lore, and story moments are things I hope are referenced or appear in future numbered titles as well. It's got a charm that's uniquely its own while also taking inspiration from the best that prior Final Fantasy titles had to offer.
It's an enormous discredit to how good FFXIV is - especially its updates - to say it's the "least original" game in the series when it's stuffed full of more original content than any Final Fantasy game I can recall. (Heck, FFXII's world of Ivalice isn't even original since it's an already established world from FFT and Vagrant Story).
Or are we going to just forget that the original Final Fantasy titles just stole D&D and classic fantasy monsters wholesale instead of inventing their own? I grew up fighting generic imps, goblins, mummies, zombies, minotaurs, ghouls, medusas, trolls, vampires, and countless other nondescript beasties long before the series started slowly added in staples like Bombs, Tonberries, Chocobos, Cactaurs, Moogles, etc.
Meanwhile, Hildibrand content alone in Final Fantasy XIV is... unique... enough to justify the whole game's existence. You probably won't find much else like it... anywhere.