The main reasons behind the dissatisfaction of job gameplay

[Aravell]

And although we saw some early grumbling about it as far back as Shadowbringers (though, at the time, it was readily dismissed)

People were so happy to dismiss any complaints as long as it wasn't affecting their main job. Like how you can clearly see people that don't even play melee jobs telling those who main the jobs that they should lose all positionals so the role is easier to pick up, for example.

Shadowbringers only massively simplified MCH and the entire healer role, so the majority of the community didn't care. "Nobody plays those jobs anyway".

Then Endwalker started on the DPS jobs. The SMN rework created a massive rift in the middle of the SMN playerbase, the SAM Kaiten removal got a lot of them angry. The DPS realise that their jobs aren't untouchable, so the grumbling started getting louder.

Then Dawntrail happened and the very well-received VPR got changes before most of the playerbase even got a chance to get better at it. Now the trust in the job design team is at an all-time low.