I can understand the arguement. sometimes it does feel like FFXIV was designed to try and be an MMO that didn't play like any other on the market. Nothing in it looks or feels similar to any MMO out there, and because of that lack of familiarity people are used to in MMO's a lot of them left or simply didn't like it. If FFXIV had been the first MMO ever made however, we'd probably be seeing other MMO's building on it's foundations instead of how the 'standard' MMO's of today build off the foundations of Everquest.
That being said though, from an opposite point of view there's been a lot of games that did release with a familiarity and 'clone style' feel to them. Warhammer Online was essentially a clone of WoW but with more advanced -open world quests- and RvR combat, and though it did well for it's first couple of months, it was doomed to failure because of the constant never-ending bugs that Mythic have never fixed.
Age Of Conan also cloned WoW's style but introduced a different battle system that although worked, wasn't enough to save the game, which again was plagued with bugs and problems, as well as many other things people didn't like.
Champions Online cloned City Of Heroes (Though to be fair it was made by the same company), and even though it was an enhanced and graphically superior game, it hasn't done as well as City Of Heroes because a lot of basic functions from CoH that people liked either weren't carried over or were 'enhanced' in a bad way.
So a lot of things that cause an MMO to fail isn't taking earlier models and making them better, sometimes trying to make it better can destroy it. Many players enjoy simplicity in their gameplay, being able to just press a few meager buttons in a repeated loop to take down anything they come across, easy controls to move around with, easy ways to craft, easy ways to view inventory, easy ways to advance your character, easy ways to level up. All the 'successfull' MMO's had these things. People like easy, and those that didn't like easy-mode found niche MMO's such as FFXI which catered more to the challenge and difficult play-style they wanted.
If FFXIV wants to survive it has a simple choice to make, it either -
1: Makes the game easy-mode, which FFXI players and many other people will hate, but will draw in other MMO gamers or...
2: Make the game hard-mode, which FFXI players and others will enjoy, but will deter other MMO gamers.
Once FFXIV's foundation has been laid around patch 1.21, whether it be an FFXI clone, WoW clone or attempting to be it's own unique thing (which is actually one of the things I like most about it at the moment), I think it needs to make this choice before continuing. The choice it makes will decide it's future.