FFXI, most importantly, suffers from lack of variety. With no real customizable equipment, and equipment that only changes in color ("palette swaps"), everybody ends up looking the same. There's no choices "Hm.. this is good, but so is this," there's just "This is the best," and it ends up in everyone looking the same.
What else makes everybody the same? The illusion that your secondary profession gives you a choice. It doesn't.
Do you want to be a Warrior who can cast spells? Sure! Be a Warrior/Mage. Will you be an effective fighter? No. Will you be invited to groups? No.
FFXI is a "cookie cutter" game meaning everybody is exactly the same as everybody else, because there are no alternatives for anything. Just one way to do things, with very few exceptions.
That, and the fact that half the monsters in the game aren't unique to themselves.
You'll go from fighting..
Sick Bunny
Crappy Bunny
Lame Bunny
Bunny
Strong Bunny
Super Bunny
Chou Omega FINAL Bunny
Ruiner of Worlds Bunny
And they'll all look exactly the same, except colored differently. That, combined with the fact that when it came out in the US, it had already been out in Japan for over a year, further isolating the Japanese population (who are largely rude to the International players) from the rest of the game.
FFXI has semi-interesting quests, below-average graphics, and is much, much too focused on forcing people to group. Another "failure" MMORPG.
The contested regions of the game are a joke--pretty much the only thing that comes from "conquering" a disputed territory is a small, insignificant NPC Vendor appearing in the city who owns it. FFXI has any number of problems, but my biggest problems with it were the problems with Alt-Tabbing, the TERRIBLE controls, and the INSANE file updates. Checking every SINGLE file, out of THOUSANDS, for a 2MB update? Yeah. That's efficient. The "PlayOnline" system is total garbage. The game wouldn't be so terrible (albeit it is still not worth playing) if it didn't have the PO system.