-the combat system with its stamina gauge and no auto attacks was horrid
-the game punished mages making no way to get MP other than expensive ethers or a trip back to an aetheryte every 2 fights making it so no one wanted to player THM or CNJ
-lacked a lot of iconic FF stuff (couldn't ride chocobos, no recognizable jobs/skills)
-a confusing class system that left some classes (namely THM and CNJ) for the better part of the leveling experience unsure as to the role as both classes had damaging and healing spells)
-extremely poor translation effort that left even the Japanese players wondering what was going on(look up horsebird fiasco which is what in beta the Japanese maps were plastered with this in the chocobo stable areas where you could inconveniently not pick up a chocobo)*
-lack of auction house