I have great respect for the Roman Catholic Church; but the notion that (very) fallible humans could decide that another human (however saintly his character, however elevated his position) was infallible when speaking on all subjects or any subject strikes me as bizarre.
And the notion that any person who is wholly human - as opposed to human and divine - was conceived immaculately is truly bizarre.
What do you think "conceived immaculately" means?
Do you believe in the Fall of Adam and Eve?
It is easier to believe that all humans are born free of sin than to believe in original sin of mankind. After all what is more innocent than a newborn. So in reality it is a matter of faith that we are all born into sin as opposed to choosing it.
The idea of the Immaculate Conception is that the Christ would not be born through woman that carried original sin. Since God decided to burden all mankind with original sin, he has every right to exempt whomever he desires from the stain of that original sin.
Also the idea is that the Pope is not infallible in all regards, only in the regards of speaking on maters of Faith and Morals. It is believed that it is not he the Pope or even the Church talking when the Pope speaks Ex Cathedra, it is the Holly Spirit speaking through the Pope. The Pope is called the Vicar of Christ because he is the “Earthly representative of God or Christ” . Yet, he is till only a man. Often a very human man with very real short comings and sometimes very many sins.