You did not read the entire post, and what you did read, you apparently did not understand. All human flesh is under the sentence of Original Sin. The Dogma of Immaculate Conception is that the Virgin was preserved from the stain of Original Sin from the moment of her conception by a prospective application of the merits of the Redemption. That is a distinct issue. To say, as you suggest, that the Virgin was not under the sentence of Original Sin would be the equivalent of saying that she did not need to be redeemed. The Church does not so teach.
Now, was it Pope -- no pun intended -- who said, "a little learning is a dangerous thing"? In any case, whoever it was, please take heed.
In short, the Catholic doctrine of Original Sin is nonsensical rubbish.
In addition, not having been around when the so called "Original Sin" was committed, I refuse to accept any guilt you or yours would force on me.