Well I've read this article and agree with him. FFXI has maybe 200,000 subs, not huge by todays standards but that's 200,000 subs for over eleven years. That's $343,200,000 made. For a game that development cost is said to be around $16 to $24 million that's not a bad return.
As for the game, it's true that they aren't trying to reinvent the wheel but that is a good thing. I read an article, FFXIV's Buffet Effect and it's true. It has a lot of the content you find in other MMO but all under one roof. The key in P2P is never letting the players get bored due to lack of content and FFXIV has content in spades.