In my opinion, SquareEnix got greedy. Simple as that. From them feeling the need to change the series in order to attract a bigger market, to the statements of wanting to have the same release schedule as Call of Duty.. it all points to them seriously misreading what the majority of their fans really wanted from them. I have to admit, most people were probably more than happy when they finally removed random battles (the most annoying thing in the world), and I actually have no problem with them tinkering with the gameplay each edition, as it's probably needed to keep the series from getting stale. But no fans ever said we wanted to remove all forms of exploration, remove the world map hub, dumb down the customization, remove all cities, shops and NPC's to interact with.. I mean, what the heck were they thinking? FF13 basically has NONE of the elements that series have been know for, at least the attractive ones. What we're left with is some corridor based, all flashy animations/no strategy or fun in combat and characters that no one can relate to. It's turned into an action adventure with RPG elements and squeemy japanese pop teens.
For SquareEnix to turn it around, the remedy is quite easy really: go back to your roots. Do what you did so well for many, many years. The gameplay mechanics are not broken, just give us a awesome new world (in the vein of IX or XII) with the freedom to explore and customize, and most of us are back on board. You'll see.