"Therefore, far above all the angels and all the saints so wondrously did God endow her with the abundance of all heavenly gifts poured from the treasury of his divinity that this mother, ever absolutely free of all stain of sin, all fair and perfect, would possess that fullness of holy innocence and sanctity than which, under God, one cannot even imagine anything greater, and which, outside of God, no mind can succeed in comprehending fully."
And, as Annalex says, there is a difference from the very beginning between the Theotokos and the rest of humanity according to Catholic teaching. This is the main point that we Orthodox have been making about the I.C., since it is not in line with Orthodox teaching, as we have explained.
The fact that our teaching on original sin means that the I.C. is not required for the Virgin to be sinless does not change the fact that the Catholic doctrine makes her beginning ontologically different from every other post-fall human.
That difference is not ontological. The difference is that her baptism and sanctification occurred earlier than for the rest of the saints. The superlatives in the encyclical refer to the superabundant merits of Christ and should not be a source of any controversy.
Required? What is required by God? What God does in the first dispensation, He exceeds in the next!
If Jesus and Mary are the New Adam and the New Eve respectively, why does the connection bother you? If three persons were born without sin, then how does the fourth one, Mary, fit in this parallelism that BOTH East and West recogized very early? If Mary is the New Eve, she was born sinless - meaning, she was born with God's presence within her. That is exactly the doctrine of the Immaculate Conception. She was born with God's presence AND she was born without the stain of original sin (stain = effect of original sin, which is concupiscence).
The fact that we agree she remained sinless through her entire life is proof that she had no concupiscence. It is impossible to remain sinless without a special grace from God. To say that Mary was an ordinary person who remained sinless by her own power is absurd. Scriptures cry out against such ideas throughout.
Regards