I don't know where you get this idea. The church always believed in the perpetual virginity of Mary, and restated it in 1854, because heretics were refuting it. Not because it wasn't true before.
...can you honestly grasp how nonsensical it looks from the outside
To be honest, I think your bias against the Church has blinded you from the truth. Your argument is nonsensical. The Church has remained constant in its belief about Mary for more than 2000 years, and if you can't see that as proof of the truth, then I can't help you. God chose a human woman to bear His son and carry Him in her womb and give birth to Him and raise Him. The bible, 2000 years of faithful Christians and common sense all hold that Mary remained a virgin for life.
I believe that God wants us to honor and respect His Holy Mother.
No argument there - I think the fly in the ointment is the extreme to which it is carried in Catholicism (excepting of course the subject of our present chat)