FFXIV since ARR has been 90%+ casual focused... and the game has been booming lately. Honestly the more things are simplified and content is streamlined the more popular the game is becoming.
To be honest I feel the vast majority of MMO players fall in the casual to very casual range and this game is designed for those players. It is not designed for mid cores or hardcore players in any way. Is there some challenging stuff... yes. But it is optional and more or less separate from the primary game.
FFXIV is a mmo for those who want to play a casual experience, in my opinion a MMO-Lite style game. This game is designed so you are not required to do anything, you are not punished for taking breaks, and you do not need to make spreadsheets to optimize your character. Progression is simplified, jobs are simplified, crafting/gathering/economy is simplified. Crafting is seperate from endgame more or less. PvP is separate from PvE. Raiding outside savage and ultimate are designed for easy clears without much prior knowledge, group coordination, and extremely rewarding in terms of gear distribution.
And Since the beginning this has been Yoshida's vision of the perfect mmo and he has not deviated at all from it. So I would not expect the game to change at all. Especially with the success it is seeing.