Increasing aetherial capacity

[KageTokage]

The ability to manipulate aether is described as being strongly tied to the soul, so it's not something that can be easily remedied if you lack an innate affinity for it. Sometimes it's simply a case of not being practiced enough, but it's also mentioned some individuals are straight up not able to use aetherytes due to being too aetherically inept to teleport.

There is still a physical component to it, though, as the Garlean inability to manipulate aether is described as being of such nature and eugenics wouldn't be able to improve aetheric capabilities were it tied strictly to the soul.

I think "aetheric capacity" is in reference to how much aether is actually stored in an individual's body, so even a Garlean could potentially have an extremely high aetheric capacity, but simply be incapable of tapping into it due to their deficiency.