It took them sacrificing half their population to essentially create something to help the shield existing on the planet already that was on the other side of the universe from Ultima Thule. Hate to see how many they'd have to sacrifice to create shields themselves to be able to last in Ultima Thule itself. They had an entelechy for only they know how long with the Elpis flower and it took an unknown amount of time for Hermes to create the Meteion before the memory wipe. Without the memory wipe of the time loop Hermes would have been the psycho nut he became and been largely useless and no one but him knew any remote way to create entelechies. Zodiark was the culmination of what they knew about Dynamis and how to stop it