It is not mentioned that the races of man only sprang up during / after the crisis, but according to Hythlodaeus Hydaelyn was created to make sure the "new world... belong[ed] to the lives newly born," rather than the Ancients continuing to lord over the planet and/or using those same new lives as sacrifices to Zodiark.
Hythlodaeus: "The cycle of life had begun anew, and we reconsidered the means by which we might protect it. The Convocation decided thus: we would nurture our world until it was bursting with vitality. Then, when the time was right, we would offer some portion of its living energy to Zodiark... In return, He would restore to us those brethren whose souls had fed His strength, and together we would resume our role as stewards. There were, however, those who disagreed with this plan. They argued that enough had been sacrificed to Zodiark - that this new world should belong to the lives newly born. These dissidents surrendered their life energies in the creation of Hydaelyn, an incarnation of their opposing belief. And for the first time in history, our people stood divided..."
The original plan was just to offer up
some of the "planet's living energy" (re: aether) to Zodiark, which presumably would have included culling the race(s) of man. While it may not have been intended to sacrifice the whole of man in the beginning, that has very much become the intent of the Ascians:
Emet-Selch: "Once the rejoining of worlds is complete, Zodiark will regain His full strength and shatter His prison. Then we shall offer up the Source's remaining inhabitants in sacrifice, that we might resurrect our brethren who died to bring Zodiark into existence."
Whether the races of man already existed in their myriad forms, whether the intent was to protect them or just stop sacrifices to Zodiark, whether the original plan was just to kill
some of man... the point is the Ascians fully intend to commit genocide on the races of man to bring back their dead. Hydaelyn's exists
solely to prevent such slaughter and genocide, so "Kill Hydaelyn to put the reins of history in the hands of man!" doesn't make any sense.
Not targeted at you, just a general critique of the #NeitherPrimal stance.
To add one last key point:
- Hydaelyn is not the will or embodiment of the Light; she is simply a primal aspected to that element. Her power to split apart and bind Zodiark stems entirely from that elemental affinity. Like all primals she presumably feeds on aether, but it's ambiguous right now how she is sating that hunger; she has either usurped Zodiark's position as the "will of the star" (and thus serves as the planet's font of aether, not a consumer of it) or isn't summoned and is currently in the aetherial plane only.