Everything.
You lvl WAY too slow and the activity itsself is the most boring thing I've ever seen in any game.
Sitting in a factory in RL doing the same stuff everyday is more interesting and diversified than this.
If I had a TV I might not mind spamming Enter all day, but since I don't, I can't even watch TV while spamming enter without looking.
I tried raising quality instead for more exp, the difference was so shallow it didn't matter at all.
If I craft with leves instead of my own materials, I spend even more time on useless stuff like running from one camp to another, having 2 leves per camp at most.
There is NO interesting, engaging content for crafters at all.
Crafted gear is inferior to NM drops until end game when you put in lots of materia.
SE could get rid of crafting classes and it would take nothing away from my gameplay.

I usually love crafting; especially cooking and sewing. I did it in any online or offline game possible and in some it was really enjoyable, not so much in others, but it always involved funny mini games, a suitable leveling curve, etc. or, if the game didn't have any of these, at least instant craft of as many items as I had material.

FFXIV though..I won't even call this a mini game..just the most tedious thing ever.
I'd rather see FFXIV take the engaging and enjoyable route, but if they can't think of anything, I'd rather have instant craft than this.