i think it really is because the ilvls increase too fast. i would like the game to have increases maybe every half a year or longer, so content stays relevant longer.
But as soon as you beat moogle x you dont go back to that fight, since after is shiva, and the possible gear drop on moogle isnt worth it for most people.
It's sad but true and it happens to everything.

Coil is even worse. after 1 week or maybe 2 (if your lucky) it's almost impossible to join people since you are not pro yet. It's a pretty sad and stupid development.
I blame the 100% scripted fights that have close to zero randomness. If they had, it would be harder to "learn" them instead you would need more skill. But its a easy way to create content. Sadly the perfect recipe for these kinda developments in the community and for fast boredom.