MMO's revolutionized the RPG genre and if you think otherwise, you're misguided. The sheer amount of content included in MMOs shows how engrossing a RPG can be. XII was one of the first to take MMO elements and apply them to a single player game. Now it has drastically affected (not just XII of course) the genre as a whole.
Example: Dragon Age.
Dragon Age is a freaking awesome game. It shares similar elements with what XII did. Illusion of an open world, party members with active combat. Etc etc.
You obviously haven't played too many MMOs because if you have you'd know they aren't all "mindless grind and repetition". Korean MMOs are, yes. Because they like the grind. But most popular MMOs, aren't. And they have a huge amount of story and content that sorry, a standard game anymore can't compete with. Check out WoW. It has the lore from the first 3 warcraft games. It has spin off books. It has comics. It is going on its 5th expansion. For one game (essentially) Any game or series that tries to emulate that amount of content is okay in my book. It makes for a more engrossing world.
Take Skyrim as another example. The Elder scroll series is FULL of lore. That series itself has been around forever and has been taking on a "MMO" feel. It goes along the same boat.
Discarding this one game because it was too much like an MMO is silly and foolish when countless other games since then were successful when playing off it. FF XII was just one of the first to do so, so it was riding a bike up hill for fans.