Another thing too is the combat system for me.
Maybe it's because I am a person that likes patterns and structure, but I like the way the combat plays especially in high-end content where you can actually plan things out and perfect it and it becomes almost like clockwork.
I like the combo system a lot too, it doesn't feel like you're aimless spamming a button or auto-attacking and waiting for a resource.
Every button you press has a direct and logical purpose and there's quite a lot of different ways to express skill.

I've been picking up BLM again and am getting into Advanced BLM and it's pretty fun to learn about.
But yeah the combat doesn't feel as random as a lot of other MMO's do.
It feels like I am in much more control of what's happening.