I understand the popularity of FATEs as a means to level. And can understand there being a question if the mechanic is valid or not. But is it actually true that FATEs are the fastest way to level, vs. a dungeon? To put it all on equal footing:

Time to run a dungeon, in a decent group vs
Time spent doing FATEs and running between them and waiting for them to pop.

(If we take out Duty Finder queues from the equation since that is a known issue which should be resolved eventually).

To ME, at least, it seems faster to do a level appropriate Dungeon than a FATE. And certainly more enjoyable then stare at map, run, target, bio. Repeat.