The general argument of pro-FATE people is that it's faster than others which makes it the only viable chance to level up.
The general argument of anti-FATE people is that it's faster than others which makes other options not viable to level up.
A general nerf for FATE would not make it impossible. It would just slow the general pace down. How long it is "appropriate" to take to get your job from 1-50 varies for each person. Some want instant gratification, some would rather work for it so each step of progress actually matters. That's up for SE to decide. Some balancing still NEEDS to be done though because as it stands a lot of other options are invalidated by the sheer XP/hour value.
Except people having a bit longer term goals instead of blazing through the content and working a bit harder to try to maximize XP gains and perhaps. Which could mean more meaningful economy regarding gear and consumables. There's the problem of vendors though. And some do like instant gratification and don't want to work for achieving something as hard as others.
Gathering is the bit that makes money. Crafting is obsolete for the most part due to a) People not needing crafted gear for the most part b) vendor prices are usually a lot cheaper than crafting material from the marketplace c) materia slotting pre-max level is just for novelty. Sure it wouldn't be the be-all end-all solution. Save for endgame most of the money seems to come from materials that crafters actually need to level up.
The economy overall needs balancing and slowing down XP gains wouldn't be the only thing that would give it a boost. In an ideal MMO world money would go from fighters' loot stash -> crafters -> gatherers and material refinement would go from gatherers -> crafters -> fighters. Now vendors make most of crafting obsolete even for that short strip of leveling up. Getting a bit sidetracked now though, apologies.