Sex isn’t a Sacrament but it is a sacramental that points a person towards them, analogous to a restating of one’s baptismal vows. Of course, in the real world, with all its misinformation and madness, only a minority are privileged to see it that way, but in its intended nature that is what it is. In, for example, a moment of mutual orgasm, the husband and wife can more readily - than any other time - thank God for the gift of union, because in sex, it has an immensely powerful natural pleasure that serves as a sign & symbol of the spiritual reality of Christ & Church. It isn’t coincidental that the sacred author in scripture chooses man & wife as this symbol rather than using, say, friendship, such as between David & Jonathan. That wouldn’t be a fully accurate sign of Christ & Church.
I’m not sure how well that could be applied to a couple in a natural marriage, but sex as a sacramental among Catholics and some other Christians is entirely appropriate. (I suppose the important part here is: yes, contraceptive forms of sex are still repugnant for non-Christians.)
I’m basing this on Paul M. Quay’s essay “Contraception and Conjugal Love” which was published years prior to Humanae Vitae but does a good job of explaining how some Catholic theologians in the past, who argued on the evil of contraception strictly on the grounds that sex in marriage is only for procreation (which it isn’t) were selling themselves short.