The best way to find a good mix for a game genre is to keep trying new things all the time. We saw Square do this countless times in the past by changing battle systems, camera styles, the kind of world the game is set in and so on. The only way a genre can grow is by experimenting, otherwise everything becomes 'samey' and stale.

From what I can tell of FFXIV, Square were not just going for a game that was completely different from FFXI, but also completely different from any other MMO on the market, this way it feels fresh, new and unique and stops people crowing 'clone' all day. It's a bold move when a company tries this kind of thing as it can cost them a lot of money, and as we've all seen it didn't work so well in some regards, but thankfully the good thing about an MMO is that it can be remade without having to create a brand new game.

Those are just my thoughts on it, not argueing with anyone, just wanted to add my little bit.