
In my understanding, the reason why the Warrior of Light is able to master so many disciplines is:
a) Ridiculously privileged political position. As a result of Minfilia and the Grand Company leaders speaking directly and personally in your favour, you are introduced to the absolute masters of every discipline (the job mentors) and learn directly from them. These masters gift you "job stones" (aka soul crystals - that's a whole other lore dump on its own, one of which was posted quite recently in another thread of this forum if you go looking), which accelerate the learning process, but are rare artefacts that are in some cases quite closely guarded. If the Warrior of Light was not the Warrior of Light, it's highly unlikely that they would be introduced not just to one absolute master and one soul crystal, but multiple...
b) The Echo. This absolutely plays no small part in helping them to learn. The Echo is also known as "the power to transcend", because at its core, it's the power to make the boundaries of a man's soul mutable. Which means that if a powerful Echo user, who was gifted this particular Echo ability by Hydaelyn (polymathy - and not all Echo users are polymaths), spends enough time around the absolute masters and the semi-sentient soul crystals for a job, they'll start just magically being able to do the thing without having to sink the hours into learning it.
Without all of these things (a master mentor, a soul crystal, the political connections to be introduced to those things, and the Echo), well...
Think about how long it takes to become, say, a fully qualified doctor. Several years of medical school, several years of working as a student doctor, several years of gaining respect and prestige... then think about how long it takes to become a respected doctor. More decades of sleepless nights, possible divorces and loss of family as a result of putting the job first, no small amount of determination and intelligence. Then think about how long it takes to become a leader in the medical field, with published papers and maybe some academic awards or whatever. Not even a Nobel Prize, necessarily, just someone who's considered an authority.
Then apply that amount of time and level of commitment to every discipline you want your character to master.
a) Ridiculously privileged political position. As a result of Minfilia and the Grand Company leaders speaking directly and personally in your favour, you are introduced to the absolute masters of every discipline (the job mentors) and learn directly from them. These masters gift you "job stones" (aka soul crystals - that's a whole other lore dump on its own, one of which was posted quite recently in another thread of this forum if you go looking), which accelerate the learning process, but are rare artefacts that are in some cases quite closely guarded. If the Warrior of Light was not the Warrior of Light, it's highly unlikely that they would be introduced not just to one absolute master and one soul crystal, but multiple...
b) The Echo. This absolutely plays no small part in helping them to learn. The Echo is also known as "the power to transcend", because at its core, it's the power to make the boundaries of a man's soul mutable. Which means that if a powerful Echo user, who was gifted this particular Echo ability by Hydaelyn (polymathy - and not all Echo users are polymaths), spends enough time around the absolute masters and the semi-sentient soul crystals for a job, they'll start just magically being able to do the thing without having to sink the hours into learning it.
Without all of these things (a master mentor, a soul crystal, the political connections to be introduced to those things, and the Echo), well...
Think about how long it takes to become, say, a fully qualified doctor. Several years of medical school, several years of working as a student doctor, several years of gaining respect and prestige... then think about how long it takes to become a respected doctor. More decades of sleepless nights, possible divorces and loss of family as a result of putting the job first, no small amount of determination and intelligence. Then think about how long it takes to become a leader in the medical field, with published papers and maybe some academic awards or whatever. Not even a Nobel Prize, necessarily, just someone who's considered an authority.
Then apply that amount of time and level of commitment to every discipline you want your character to master.