The story I told has nothing to do with what you wrote. For your info, the very first title the Church used for Mary was “Mother of God”. This was some time in the 3rd century at a council of Ephesus (present day Turkey). Even that far back, Mary was thought to be sinless. They did not make a big deal about it because it was generally accepted and the Catholic Church did not have to compete with another Christian faith.
What happened in 1854 was different. The Catholic Church had to make a formal statement as to its belief regarding the mother of Jesus. The Pope therefore declared ex-cathedra (from the chair of Peter, and therefore infallibly) that Mary was untouched by sin from the moment of her conception by her parents — it’s just that simple.
There is nothing, as I've said before, prior to the 4th century and Christianity becoming the religion of the Empire, in the writings of any of the early church fathers that in any way promotes any current, Catholic, Marian doctrine or could really even be seen as the basis for it. Once she was declared "Theotokos", and the religion becomes the religion of the Empire, then you see all the pagan influence - the worship of goddesses - become established in the Church as they begin to latch on to Mary. Combine that with the belief that God (and Jesus) are harsh, judgmental kings - who one cannot possibly go to in prayer, themselves - and you see the need for the gentle, feminine, "mother" figure to go to God and "intercede".
Again, show me something in writing from the early church fathers, prior to the 4th century, that in any way promotes Mary as the Immaculate Conception, speaks of her Assumption, shows that she was an object of prayer or that anyone thought she should be prayed to and could "intercede", and I'll take it all back. As a matter of fact, I don't believe there's anything to even indicate that anyone thought she didn't have normal relations with Joseph after the birth of Jesus, either.