Without good job design it hurts the Replayability the most, If every job plays very samey then what's the point of redoing content on a different job for a new experience, you've already done the "Content" you will get the same gameplay experience playing a Different job so it becomes just more bland to even do a fight on a different job, Which in turn actually hurts the content you are going through.
The fundamental Issue with EW as I see it was Always Job design, if Jobs were more fun and varied then it would take way longer if you played more jobs to get bored during a dull moment during a patch cycle. Leveling and learning jobs would be intresting, Ect.
Even one key issue, early level jobs being fixed would at Least make it so players would actually have fun synching down and doing old content, but it's just not fun or satisfying enough at 50.... 60... even 70 for a lot of jobs.
The content can be good, fun but the Jobs are what makes the game Interesting and unique, they're quite literally a core fundamental of a MMORPG, but Job design has been ignored for the sake of easy balance to avoid one job slightly underperforming, Healers are designed around healing but don't need to heal most the time, Tanks have become over time more easier DPS wise with no aggro management, Ranged losing most utility outside of buffing flat damage numbers, Even Melee feel a bit samey to me having very similar buffs a lot of the time getting more basic, ect.
It's really not a surprise anymore that jobs will likely remain in the 2 minute meta, Healers will stay the same, tanks will say the same, I think the statement was more that no fundamental job Ideals change, as a Tank player I can only hope that fight designs actually take into account tank mitigations and healers heal kits more at the very least but that's a stretch.