We stopped a relentless AI that was going to kill everyone on every Shard and take their souls, what then? Would she go into space and do the same to other planets? Her plan wouldn't last forever and it was just holding back the end. We saved lives at the end of the day, the memories were just that memories. As was explained in lore time and time again the Soul has to return to the Atherial Sea and be allowed to be reborn, the Endless can never return to the sea and their souls sadly were lost to that sea