A potential rework to the level-sync system.

[ItMe]

So why not reward them for reaching the endgame and just let them use all of their skills even in older content?

We just had a thread on this start not 2 weeks ago.
If you wanna read up on what was discussed, you can check it out here:
https://forum.square-enix.com/ffxiv/...evel-Synced%21

tl;dr, Having a skill synch system would be a nightmare and we should probably never expect them to add something like this to FF14.
To quote the most upvoted post from the thread:

That can not work in a balanced way. Lets use your BLM example. I get sent down to halitali in a leveling roulette on my lvl 80 BLM, and the roulette matches me with a lvl 20 THM. We get to a boss. He casts Thunder, i cast Thunder 3. Thunder 3 does the same damage per tick as Thunder(so far so good), but T3 lasts 2 ticks longer plus its initial hit is 40 potency higher AND it has a chance to proc thundercloud. You could do some math to find a balance point for the ticks and initial hit, but the fact that i get to wait 6 extra seconds before reapplying is a real advantage and if it can still proc at all(even at a reduced percentage) then the lower level caster can never catch up on damage - and thats before you account for the fact that my gear is sync-maxed and his is likely a mix of poor quality stuff that already puts him at a disadvantage. Enough DoTs, direct burn is the BLM specialty. So you nerfed my F4 to compensate. You say i can just use the old skills? Ok. Im spamming F1 for the same damage as the other guy. But no, i have 3 stacks of AF and he can only get 2 stacks(plus im running Eno and he doesnt have that yet). I can still end each round with a Despair - he doesnt have anything similar. I can pop manafont to extend a burn session, use ley lines for that sexy speed boost, drop manawall to ignore some mechanics, use xeno sharpcast triplecast and swiftcast to do damage on the run - he has swift and none of those other options. Oh, and lets not forget your umbral phase. When his mana is out he needs to use transpose and wait 7-12+ seconds before he can transpose back into his astral phase(needing to rebuild his stack). I use B3, have all my mana back in 4-8 seconds, and can F3 back over without losing my stacks. And thats just single target, we're ignoring the imbalance of an AoE pull where i can multi-dot and he cant, where i have multiple useful spells and he doesnt, and where i can still swap astral/umbral at full stacks and he is stuck with transpose.

And all that is for a DPS class, seemingly the easiest to balance. How do you propose we balance Group A having a healer who can only cure 1 and medica 1(both on GCD, both with a cast timer, and no other options) against Group B having those same options, plus stronger versions, plus 9 instant cast heal spells with varying traits(including shields, regens, aoe heals, and a full heal)? Oh, and the second groups healer has 3 AoE damage spells(one of which has an attached stun, another of which has an attached heal), and the first group has none.

Final note, i also disagree with the OPs assertion that the level sync "completely wipes out any feeling of progress". I feel like if anything, it re-asserts just how far youve come. Your character used to struggle just to do a 2 hit damage rotation. Now you have a 15 move opener sequence you do that is optimized to the nth degree. Looking back occasionally really helps that feeling of progress.