How hard do you think it is? I used to think that if the Great Warriors were to climb again they would reach it in no time but with all the reveals from the spin-off(creatures and other beings sealed) + the Red Dump I am not sure anymore.
It looks like the Zahard Empire is "stable" because they removed all the biggest threats.
I have so many unfinished paragraphs addressing TOG lore in my notes. Lol, Yea they include some of the ideas you are mentioning.
The 13 GW were special & strong. They faced challenges, & I believe as they became corrupted; Forces, individuals etc that they feared, contended against, was against them. They either killed off or sealed. That also leads me to believe they just aren’t all powerful, they monopolized power. There may be just a few forces capable of growing similarly strong…..Machines, Plants, 1st Human, Ancients, etc etc