Do you think after Endwalker there will be time travel?

[Cabalabob]

Yes and no. The Soul Crystal does act as a skill repository from past practioners of that Discipline that a user can draw skills quickly from, but you're also creating skills yourself as you go along, which are then recorded in the Soul Crystal, via a process similar to attuning to an aetheryte. And MCH and BLU's Soul Crystals you are literally creating everything from scratch then and there, given both Jobs have been made virtually from out of whole cloth unlike other Jobs that are just Disciplines that had been lost, forgotten, were foreign and unknown in Eorzea or made illegal.

MCH is the WoL testing Stephanivien's new theories of aetheromachinestry derived from Garlean magitek that he melded with a few Limsan musketry techniques (from the strictly controlled/forbidden Discipline of Musketeer), while BLU was actually a fake Job (but based on a real one from the New World) peddled by a con artist that we actually made completely functional, much to his relief, given the Limsan authorities were circling.

So the WoL is not just 'drawing on older techniques', they're actually adding new ones they make up themselves, and other NPC practioners of the Jobs are shown doing the same thing, making use of skills and spells we have no access to (and never will). Most of our combat knowledge and skill just comes from plain old determination and a bountiful reserve of personal aether, something the Soul Crystals only enhance and amplify (that the Echo and the Blessing of Light enhance even further).

Yes we’re adapting the fighting style but we’re building it on a foundation that we don’t actually know. This becomes abundantly clear if you unequip your soul Crystal. You can see that, for example, as a gladiator all we know is our 1-2-3 combo, total eclipse, fight or flight, shield bash, shield lob, iron will, sentinel and circle of scorn. These are the only skills that we properly know, everything else comes from the soul Crystal and without it you simply can’t do them anymore, even skills that realistically there’s no reason you shouldn’t be able to as a gladiator, like goring blade.

Again this could be taken as the lines between narrative and gameplay becoming skewed since they simply abandoned classes as an idea so they don’t update the base classes anymore. But it does make sense from a lore perspective since as lanadra says, it’s hard to imagine we mastered all these fighting styles, it makes more sense that we’re using the soul crystals to cheat.

It’s also interesting to think that the soul Crystal is actually hurting our growth, since we’re no longer developing our own skills and instead are becoming dependant on this lump of rock. If we were to ever lose it or have it taken from us we’d have nothing. Kind of like what they did with midgarsormr locking away our blessing of light.