A protestant wrote the following heresies:

“Mary is, and was, nothing but a Jewish maiden who met the requirements Yhwh set through whom to gift humanity with the greatest blessing of all eternity: HIS SON, our Redeemer! She lived and died as a Jewish girl of her time. She was blessed to be chosen for the honor bestowed upon her, but she was no more than any other young woman of her time, and when she died, she was buried like all her peers. Not "immaculate", just a virgin, and believer in Him! No human since Eve, even started out " immaculate", let alone remain so to child bearing age. She undoubtedly kept kosher, but no greater status than others who did so. It was her DNA, and ancestry that mattered too.”

Answer:

God's requirement was that she was immaculate: God can't mix with sin, which is a chain to Satan. God is perfect love, can't "mix" with anything stained with sin, imperfect.

God is almighty: God could preserve Mary from original sin, God did it.

How exactly? search for the term seed in the Bible. He too the seed of Mary from Adam before original sin, then re-implanted it in Adam. This seed was transferred with the blessing, for example from Abraham to Isaac to Israel and all Jesus’ genealogy (the jumps in the genealogy are when the angels took it to the Ark of the Covenant, then back again).

That's why she is "the" Immaculate Conception, "the New Eve" as the first Christians called her (Jesus is called the “New Adam” in the New Testament).

Adam, Eve and Jesus were immaculate but not conceived (Adam and Eve did not evolve from a monkey!). Mary is the one and only Immaculate Conception and she will be the only one until the end of times: God is super-efficient: He didn't need to preserve anyone else to be incarnate.

Warning: the following are speculative answers could contain errors and are thus subject to the authority of the Church.

Why didn't God preserve all of us from original sin?

Imagine this is a sports match or videogame against Satan: there are rules. In "the economy of salvation" or damnation, imagine that every supernatural intervention of one side, gives the right to intervene to the other side. The more supernatural, the more points it costs. Where do the points come from? From us choosing Charity or sin every second. That's why abortion and homosex are tilting the game right now: they are sins that call out to Heaven (they cost a lot of points to repair the damage to Divine Justice, that's why the general level of grace in people is decreasing: less prayer, less graces are applied to recover the sinners).

Why didn't Jesus incarnate in Eve?

It would have been easier to save a handful of humans, right?

Before creating the Universe, God saw everything that could happen in all possible alternatives, He even saw the fall of angels and man and how God the Son would offer to redeem us. Among all possible universes and creatures and body plans and... every nuance you might think of, in His infinite Wisdom and Providence, He chose this.

If you were God, wouldn't you pick the best, the perfect mother? Of all possible women in the history of mankind, God chose and created Mary. God can't do anything imperfect and can't unite with imperfection. That's why in His Mercy, He created purgatory to Purge our imperfections and allow us to present ourselves with the white unblemished robes.

Couldn't Mary be born from Eve?

Of all possible grandparents for Jesus, God chose Saints Anne and Joachim.

Couldn't Jesus's grandparents be born from Adam?

No. Children are the fruit of marriage. Different marriages, different fruits. Only the great-grandparents of Jesus were capable of generating the grandparents of Jesus... and so forth.

If God could choose the best father on earth, why did he leave Joseph with original sin?

St. Augustine says that original sin is transmitted by the seed of fallen men. It wasn’t necessary for Joseph to be immaculate because he was not going to be a father through sexual relations, being both consecrated in celibacy to God, as proven by the Bible.

The Holy Spirit acted in the name of the Father. Joseph was an adoptive father. Jesus was begotten from the Holy Spirit and Mary, not Joseph. As explained, in the economy of salvation, it was better to use those scarce graces in other priorities, and not preserving all Jesus family-tree up to Adam.

Nevertheless, theologians say that Joseph was cleansed before birth from original sin: if St. John the Baptist had that prerrogative in order to baptise Jesus, the more necessary for Joseph, who was to hold, dress and nourish Jesus.

Also, God harvests more good from evil (original sin), than from just good.

Why didn't God intervene just before original sin, preserving Adam and Eve?

God respects freedom to love or not. There's no real love without freedom to love. To behave like robots, he already created the bio-robots, the animals programmed in what we call instinct.

God always reaps more good from evil having in mind eternal salvation.

God’s mere presence would have prevented original sin and Satan could have argued that He cheated their freedom.

Why didn’t God create Joseph and Mary instead of Adam and Eve?

Because there’d be no mankind except Jesus, Mary and Joseph, who consecrated their celibacy. God is fruitful as the number of stars or sand of the sea!

Why didn’t God create Joachim and Anne instead of Adam and Eve?

There’d be progeny apart from Mary and a fruitful mankind, right?

Before creating this perfect universe, God imagined each one of us with name and surname getting the gift of life from our parents, being a particular cell with a particular position in the mystic Body of Jesus.

God saw Adam and loved him before creating him. If he had replaced him by any other man, then there’d be no Adam and God wanted and loved Adam as Adam, the first man physically made directly by God, not the son of someone else, just as He wanted and loved each one of us, where He placed us in our family tree.

God created all angels at once, because there’s no space-time constraint for angels (that’s why their test was “instant”: whether they would serve or not “a woman clothed with the sun, with the moon under her feet, and on her head a crown of twelve stars” of Rev 12:1).

Being our immortal souls inserted in space-time and incarnated at the moment of conception, the order of precedence is essential, because our bodies don’t come directly from God, but by the mediation of our ancestry. There’s also an the order of precedence for each of our cells since conception. That’s an analogy to what God did to create His mystical body from bodies constrained by succession in time.

How is it possible that the man-God, head of the mystical body, came from a woman who is supposedly a part of that body?

Isn’t like a chicken-egg dilemma? (by the way, evolution theory can’t solve it still) 1

In the space-time restriction physical Mary-then-Jesus, but in eternity God-then-Mary. Physically, dressed with the robes of the fallen nature, they are two distinct persons with different bodies, but mystically Jesus is the head and Mary the body and each of us a cell of Her body, the Church, but at the same time, the other side of the coin: Mary is the mother of both the Head Jesus (Mother of God) and the Body of Jesus (the Chuch).

Can God really guide all generations according to His Will?

Matthew 1,17

Thus the total number of generations from Abraham to David is fourteen generations2; from David to the Babylonian exile, fourteen generations3; from the Babylonian exile to the Messiah, fourteen generations.4

"Fourteen is the numerical value of the Hebrew letters forming the name of David."

Note: in the second section of the genealogy (Mt 1:6b–11), three kings of Judah, Ahaziah, Joash, and Amaziah, have been omitted (see 1 Chr 3:11–12), so that there are fourteen generations in that section: could this be a result of the transfer of the seed to the Ark?

Is it just that God preserved Mary and not the rest?

What really matters is reaching Heaven with the largest heart possible. The rest is history, literally!

God reaps the best from the worst, for the salvation of souls. Suffering is not His fault but Satan’s, who made us expelled from a zero-pain full-bliss Paradise. Yet, in His Wisdom, suffering can be an advantage to help us detach from the earthly matters.

Mary’s preservation from original sin was essential for everyone's salvation, not the rest.

Also, Mary deserved her graces by fully corresponding to God’s in order to become “full of grace”:

Regina Coeli: “The Son you merited to bear” 1
Salve Regina: “Almighty and everlasting God, Who by the working of the Holy Spirit didst prepare both body and soul of the glorious Virgin Mother, Mary, that she might deserve to be made a worthy dwelling for Thy Son...”

Was Mary the super preter-woman?

The Visitation feast reminds us that Mary, descended to co-save us. Being immaculate, she had the rights to preternatural super powers (immortality, impassibility, bilocation, perfect wisdom, etc.), just like Eve in Paradise before sinning, but more, since she was to be the Mother of God!

She even had the right to enter the garden of Eden, still guarded by angels.

It’s obvious that she gave away those rights and humbled herself to the cloak of our mortal fallen flesh, to suffer for us … just like Jesus, the New Adam.

Through Jesus, she became the Eucharistic woman.

In sum, she wasn’t just another maiden, but The Woman of the Apocalipse, the most amazing perfect woman in history.

Footnotes

1 https://www.npr.org/2023/06/17/1182941234/scientists-are-still-trying-to-answer-the-age-old-chicken-or-the-egg-question
2 1. Abraham, 2. Isaac, 3. Jacob, 4. Judah, 5. Perez, 6. Hezron, 7. Ram, 8. Amminadab, 9. Nahshon, 10. Salmon, 11. Boaz, 12. Obed, 13. Jesse, 14. David the king.
3 1. Solomon, 2. Rehoboam, 3. Abijah, 4. Asaph, 5. Jehoshaphat, 6. Joram, 7. Uzziah. 8. Jotham, 9. Ahaz, 10. Hezekiah, 11. Manasseh, 12. Manasseh, 13. Amos, 14. Josiah.
4 1. Jechoniah, 2. Shealtiel, 3. Zerubbabel, 4. Abiud, 5. Eliakim, 6. Azor, 7. Zadok. 8. Achim, 9. Eliud, 10. Eleazar. 11. Matthan, 12. Matthan, 13. Jacob, 14. Joseph, the husband of Mary.