Honestly I disagree and agree with this.

On one hand synching down is annoying when you have like 8 main abilities at level 50 and your job feels awful, but on the other hand I don't really like the idea of just having massive potency op skills or super strong tank defensives in early content. I think the solution is clear, let jobs have their core skills by level 50, including all rotational skills.

As a example I'll give Paladin, a job i think is super awful currently in lower content to play as.
1. Give "magic" skills early weaker versions, this being a early version of holy spirit with the core system of gaining one after a attack, also likely having a eariler version of req.
2. same goes with atonement you can have 3 sword skills that would be weaker versions of the combo
3. Give a little bit of sustain to sheltron or holy spirit, theirs no reason why Paladin should wait until 82 for any sort of sustain while other tanks get it way earlier, it doesn't need to be as much as it has at 100 either just equivalent to something like GNB.
4. Gap closer being lower (all jobs should get them pre-50), one charge is fine as its lower.

Now the job feels similar at lower levels, I'm sure it would need some number tuning, let expansion abilities be flashy upgrades and stuff, let jobs have their core class kit, you can apply these sort of changes to other jobs too, surprise surprise jobs would actually feel good now in early content, without having that factor of having over buffed skills in early content.