Arguing the ethics of Venat's actions is completely beside the point. Everyone acknowledges it was a terrible thing to do.

The question Venat asks is existential in nature, not moral. "Is it better to suffer in the pursuit of fleeting happiness, or live in eternal yet ignorant bliss?" Ultimately this isn't even a question though; nothing lasts forever, and you can't unring the bell. Now knowing the world isn't just sugar and rainbows, the Ancients could never go back to their "paradise" no matter what they sacrificed or whether or not Meteion was stopped.

Never mind the fact their "paradise" never existed to begin with. Suffering was always there, they were just largely ignorant of it... Erichthonios appears to be in a great deal of emotional pain over his mother's death and his father's indifferent attitude toward both him and his mother's passing, for example.

... and raising creatures for the sole purpose of sacking them to Zodiark for their selfish desire betrays the Ancients' (self-appointed) mission as stewards of the star, does it not?