I think that's the point the whole story in Ea is trying to make. We're able to use Aether and we can find ways to combat this that makes sense in our own understanding. We can't understand specifically why it wouldn't work, as told by Ea with our current knowledge. Besides, they don't need weather since they function without corporeal bodies. That implies the problem extends beyond the problem of what aether can naturally change.
Also you have to remember, Hyadelyn doesn't know the full extent of the ability of Meteion after she left Etheriys. She only knows Meteion was going to doom Etheriys, so she tries to setup life elsewhere as a contingency plan. We only know Metetion traveled to a lot of stars, not the full extent of the world. She doesn't know that this was the last Bastion of the world - as told by Midgardsomr after he arrived and the world has already been sundered.
Venat specifically said she knew she was a monster. She also stated she would've never sundered her people unless she saw no other way to proceed - which means she hasn't found a solution even after we left in the circumstances following our departure. For Venat, it's a worse death to rely on Zodiark and attempt to Forestall the Final Days and then wait for the eventual end than it is to find a way forward and continue living. After all, Zodiark only accounts for half the population of the Ancients in Etheriys (not the entire universe), and Dynamis is in a much greater amount than what Zodiark can ever achieve with Aether.
Hyadelyn was no saint, and we can see that when she subjected people to suffer. However, following the sundering, if it wasn't for her, we would've been dead regardless by the Ascian's rejoinings. Take it what you will. A hero isn't a hero to everyone, but only to the ones they are saving - and that was heavily explained through the viewpoints of Emet, Elidibius, and the WoL / Scions in ShB. Venat may not have saved the ancients, but she did her duty as an Ancient to continue & improve life on the Star, which was the ancient's first and foremost goal, even though the means were an extreme way to get the result.
At the same time, you were already entrusted the legacy to safeguard the future of the Star by Emet (which people somehow forget). The ones already aware of the future have already accepted their end at the finale of Ktisis Hyperboreia and left it up to you to solve the problem of the Final Days. In that regard, the ones who are about to forget everything fully accept the outcome and pass on the responsibility to you to figure out.