I find it sad they didn't make a real MMORPG out of it.
Actually, they tried to do that. It was limited to Japan only, but it failed. The problem was that, just like with a Pokemon MMORPG, there was too much they'd have to put in and maintain if they wanted it to be authentic. The number of player customizations, player types, weapons, armor, equips, monsters, and land combination (the lands would be the largest problem by far) would take years upon years upon more years to come up with and not be crappy, if they wanted it to at least look at the standards of the G.U. series.
On a different note, with Guilty Dragon: The Sin Dragon and the Eight Curses, they've gotten rather close to an MMORPG, though they've limited the interactions with other players and made it essentially a bunch of mini games, lowered the customization, and created a fight system like a crazed "rock-paper-scissors."