However, the act of Original Sin was necessary. Without it, Adam and Eve would have been just like God's angels, lacking in free will and higher thought. They would have remained automatons, but with the knowledge of good and evil, they now had freedom to act. This freedom also allowed them to procreate, and now Adam and Eve could have children, and could multiply.
This then begs the question of, what was the purpose of such a convoluted method if God could already create life? Why was Lucifer punished if, being an angel, he had no free will of his own, and was acting in accordance with God's will, as he was performing duties he had been created to do? Why create a perfect world, only to ruin it? Why did God cause so much pain, a pain that continue to reverberate through today?
This is what Dies Irae is, a philosophical struggle to decide whether there is free will, or whether everyone is a victim of predestination. If things are predestined, why take action? If one isn't exposed to predestination, are they still acting in accordance to free will, or blissful ignorance? If someone is exposed to predestination, does continuing to act like they have a choice show blind pigheadedness?
The truth is that it's quite easy to see who a person is, or will be, very early on. One famous social test is forcing children to wait an hour before eating one Oreo cookie, and if they succeed, they get two Oreo cookies instead. Those who complete this task are much more likely to succeed in life, because they have foresight. But, if they have foresight to see what's ahead, wouldn't that mean the future is already planned, and they would have succeeded anyways?
Star, playing the role of Lucifer, was meant to have absolute agony and be the result of her own downfall and damnation. Everything in S2 is basically her fault. Every failure, every misstep, every loss can be chalked up to Star behaving like Star.