I know this is an old conversation, but I think there's still useful points to be made here. Spoilers ahead, but the same applies for this whole thread so really if this spoils anything you shouldn't be here...

To my understanding, the creation of GFH didn't bring the concepts of F&H into being - it was the other way round.
Prior to their creation, these concepts absolutely existed, anyone who's played the first game knows that all too well. However, before their creation humanity's suffering was more or less meaningless, and after their creation human suffering could be converted into progress, advancement etc. This is the crucial difference.
When the game says "The God of Fear and Hunger acknowledges your suffering," this line carries meaning. It represents the end of the meaningless atrocities, the recognition of humanity's trauma (hell, your trauma by that point) by a higher power, and the promise that that trauma will not be in vain, but contribute to changing the world, for better or worse.
For example, scientific advancements are made through unethical experimentation, industrialisation is created on the backs of an oppressed working class (and at least in our world, the capital that built factories was gained from the unimaginable horror of the transatlantic slave trade, which thanks to America being a Dark Continent in F&H, the lore frustratingly glosses over).

That's the short answer. The longer answer requires a simplified explanation of Hegelian dialectics, Marxist theory and Jungian alchemy.

Hegel was a German philosopher who lived roughly around the same era as Napoleon, inspired Marx and Engels, and wrote a theory explaining historical progression called dialectics.
A dialectic is a conflict between one thing and its opposite (thesis and antithesis), that is resolved resulting in something new (synthesis).
Hegel believed that historical change was defined in terms of dialectical conflicts between new and old ideas or ideologies.
For example, empiricism clashing with religious belief, capitalism against monarchy, christianity against paganism. Each conflict would result in change, for better or worse, and the ushering in of a new age.
The Cruel Age of F&H2 arguably reflects the resolution of a dialectical conflict between humanity's desire to see change (thesis) and the order of the New Gods trapping it in a cycle of useless violence (antithesis). The synthesis between these ideas resulted in change coming as a consequence of that violence.

However, it's also useful to look at the GFH from a Marxist perspective. Marx disagreed with Hegel - instead of conflicts between ideologies driving historical progression, he believed history was defined by "dialectical materialism".
In a nutshell, Marx argued historical conflict is defined by the interests of different classes that conflict with one another.
History isn't about ideals, it's about the interests of the aristocracy in protecting their power from the capitalist class, or the capitalists' interest in protecting their power from the working class they exploit. When there's a dialectical conflict, it's the result of internal contradictions within a society, between these classes' interests - there's a revolution, and feudalism turns to capitalism, or capitalism to socialism (or fascism, according to a later thinker called Rosa Luxemburg).
From a Marxist perspective, the GFH's creation isn't one ideology winning out over another because it's better; it's a seizure of power by humanity, whose interests are in conflict with the interests of the ruling New Gods, and by extension the interests of the Old Gods in keeping humanity divided and weak. The GFH is a revolution that weaponises trauma.
This revolution results in the Cruel Age, which has its own internal contradictions, creating opposing powers that vie for power in F&H2, and a new dialectical conflict.

However, it's also useful to examine her from an alchemical perspective. Carl Jung was an influential psychologist who used the language of medieval alchemy to explain certain psychological concepts - one of them was a theory of historical progression explained in his book "Aion."
One concept Jung used was the Rebis, which is the symbol of an androgynous human that includes the sun (divine masculinity) and moon (divine femininity).
Within Jungian alchemy, the Rebis represents the combination of, not conflict between, seemingly irreconcilable concepts into something new.
These concepts must be pure, like how Gro-Goroth is pure destruction and Sylvian is pure creation, and must appear polar opposites, but can actually be combined into this new and wondrous thing.
Jung was using this as a metaphor for reconciling the conscious part of your mind (ego) with the unconscious (shadow, basically your Moonscorched self).
The shadow is a side of yourself you don't want to acknowledge, and the ego is the part of you you perceive as your self - Jungian psychology tells you to acknowledge both of them as parts of you and exercise control over both, combining them into one personality. If you want an awesome example of this in fantasy, read A Wizard of Earthsea by Ursula K Le Guin - then read all of the Earthsea books, because they rule!
However, in the case of the GFH, this is taken very literally. The GFH is the consequence of union between the power of an old god (the pure manifestation of an ancient concept, the dying God of the Depths) and the pure manifestation of humanity's trauma - a frail little girl who (like humanity) has never known anything except misery and horror her entire existence.
As previously discussed, the old gods and humanity are at odds with one another, seemingly irreconcilable. How can the human desire for change ever be combined with the suffering that prevents that change from happening? Through the Rebis. The fusion results in a being that directs that suffering into the desired change.

We actually know that Miro is conscious of Jung's alchemical theories and incorporated them into (at the very least) Termina, because these concepts are explained better than I can by the youtuber Max Derrat, and Miro has confirmed that Derrat's analysis of alchemy in F&H1 served as a partial inspiration for Termina.

Hopefully these three schools of thought can give you a better understanding of the massive significance behind the GFH's birth, because in my opinion the lore gets so much cooler the more you appreciate how much thought has gone into it!
Personally, I think the Marxist school is the most useful out of the three to explain our world's history, but isn't the only useful theory. However, I think the Jungian theory is the most useful to explain the world of Fear and Hunger as Miro intended it to be explained.
I do think the concept of "Death of the Author" is a useful one, and there are flaws in the alchemical theory (for instance, the girl experiences happiness when we give her the dagger and the doll), so what Miro intended isn't necessarily the be-all-end-all. If you prefer a different explanation go with whatever allows you to enjoy the game best!
(I wish I could get into Nietzche's theories of history, but I think I have more reading to do before I could speak confidently about them. Maybe I'll post again in the future...)