For what it's worth...
I'm an Anglican; I have no special need to believe in the Immaculate Conception, but no particular grounds to be required to doubt it either.
I would observe that the Perpetual Virginity of Mary, a separate Catholic doctrine (shared with others, BTW) is being confused with the I.C. here. The I.C. simply says that Mary, unlike all other humans, was conceived without original sin, that the human tendency to sin innate in us since the Fall was not transmitted to her. She was conceived by a normal act of marital sex between her parents, not herself a virgin birth.
Even many Catholics, however, in attempting to honor Mary, fail to recognize the Church's teaching: like all the Faithful, Mary was saved through the grace of God mediated through the Atonement of Christ. The difference is that in the Catholic view, this worked "retroactively" -- since God is indeed master over time like all other created things -- to save her from conception onward, in order that her womb would be a sinless dwelling for the Incarnate Son. Like many another Catholic dogma, it needs to be seen as Christocentric, focusing on His Incarnation and Atonement, and His redeeming work.
As I noted above, the question of the I.C. is tangential to my own faith. But taking it as detracting from a focus on Christ is, I think, a mistake, and one we should avoid.