Wonder if anyone else has connected this but I was thinking there about how Garleans are unusual in that they're unable to use magic. Before Shadowbringers this was something that was unusual and unexplained but considering what we learned this possibility is certainly plausable.
Garlean's are unable to use magic ultimately because of Zodiark, the reason being that they're in fact the direct descendants of survivors of either Amaurot or other cities from the wake of the Final Days, the main reason being that when Zodiark initially acted to "rewrite" the laws of creation as such it meant that in order to supress the final days it meant blocking their ancestors ability to use creation in order for them to stop unwittingly summoning their deepest fears. It also explains why Garlean's are one of the largest races in general as well. Now this might not have affected every single being (as this would have affected Hydaelyn being summoned) but the majority of the populace at that time. It may even have been intentional that not everyone had their ability to use magic suppressed as the intent was to stop the Final Day's spread at large and certain individuals would have either needed their magic abilities or were able to keep control of them as they had enough skill to not give into their fears.
This would also explain the why other races are still able to use magic as they came about after the second sacrifice of the ancients in order to restore life to the near dead star and as a result they weren't affected by the original action of Zodiark to suppress the Final Days. The initial action of Zodiark might have not been a permenant measure either but a temporary one but unfortunately this was never rectified due to Zodiark and Hydaelyn ended up having their massive fight ending in the sundering and this ultimately meant those ancient Garleans ended up carrying this magic block to the modern era.
It ultimately explains why Garleans are the unusual standout's when it comes to being unable to cast magics and manipulate Aether to this day.