Limit To Power.
The demorgorg system is dangerous to both entities despite all the advancements that Legion has made to streamline the process. It is not as dangerous as the situation Helios was in when he tried to break through and assimilate the Celestial power of the sun god, but these people are no Helios.
Helios was trying to become a transcendent while absorbing the divine power of a Celestial. The giants on the other hand are already transcendents but the tree father had to make the process more dangerous to the demons for the giants of order to have this level of survival.
Now if the danger to both giants of order and demons is eliminated completely, the demorgorg system will still become obsolete because it has a limit of power. The highest rank achievable for the demorgorgs is five stars. That is the equivalent of a titan of law and it requires a living demon lord to be sealed within a transcendent.