The Church has not changed Her teaching on sex being a marital duty even when one spouse does not want it. Sex is absolutely still a duty of marriage. In fact, refusing to consummate the marriage makes even a valid marriage dissoluble by the Holy Father. The Church has only changed the tone of the message to arrive at something I think makes Her teaching more understandable in the minds of the rank-and-file.
I think you’re trying to get at the idea that Mary would somehow be “degraded” if she and St. Joseph had been physically intimate. This is not the case.
catholicnewsagency.com/resources/life-and-family/marriage/the-meaning-of-catholic-marriage/
"The preparation of [the book] Marriage actually began in 1923 when my husband gave a lecture on marriage at a Congress of the Catholic Academic Association in Ulm, Germany. The lecture was a resounding success.
In the lecture he argued that one should distinguish between the meaning of marriage (i.e., love) and its purpose (i.e., procreation). He portrayed marriage as a community of love, which, according to an admirable divine economy, finds its end in procreation.
Even though official Catholic teaching had until then [1923] put an almost exclusive stress on the importance of procreation as the purpose of marriage, the practice of the Church had always implicitly recognized love as the meaning of marriage. She had always approved the marriage of those who, because of age or other impediments, could not enjoy the blessings of children.
But conscious that he was breaking new ground in making so explicit the distinction between the purpose and the meaning of marriage, my husband sought the approval of Church authority. So he [the article author’s husband, who wrote Marriage: The Mystery of Faithful Love ] turned to His Eminence Cardinal Pacelli, then the Papal Nuncio in Munich. To this future pope (Pius XII), my husband expounded his views, and to his joy, received from the future Pontiff a full endorsement of his position.
Cardinal Pacelli’s approval coupled with the success of the lecture on marriage encouraged my husband to expand and develop the lecture into the small volume which you now have in your hands."
I in no way wish to disparage Mary, my point is that sex has not always been a prerequisite of the Church to make marriage licit or sacramental. On the other hand, in my time working in the diocesan marriage tribunal, I am aware of marriages for which an annulment was granted on the grounds of non-consummation.