It probably sounds like a really minor, really silly reason to quit, but if job balance continues to be so skewed and balance changes taking months to years, with some just being pushed to the next expansion, I can see myself quitting.

We've had the same Ninja+ Dragoon+ two ranged physical meta for all of HW and now seemingly all of SB with Summoner just barely creeping up.
Tank balance is still a mess and DARK won't be fixed until 6 months or the next expansion, and healers were doing good until these recent AST changes, which now sees things going in a similar direction to 3.4...

I understand there's no such thing as perfect balance, but this has just been an ongoing thing with no meaningful change in sight.