I think it is safe to say that men's and women's "natural / primary" roles throughout history in most societies can be described as "provider" and "nurturer" quite accurately - even though the vast majority of women throughout history also have worked "outside the home". (The idea that women traditionally have stayed home and raised the kids while the men worked outside the home simply isn't supportable. Not working for compensation of some kind is a luxury, and most women throughout history have not had the luxury of even considering not working.) Defining "primary" or "natural" roles is not a comment on anything other the historical result of differing biology, since men generally have been bigger, stronger, faster, etc. than women - and women always have been vulnerable due to the effects of pregnancy and childbirth.
Given that reality, it is understandable to frame the "natural / primary" responsibilities given to men and women ("by God" or "by nature" - whichever you prefer) in that light. The interesting thing about the Proclamation to the World, in my opinion, is that it appears to lay out this "natural" distinction and then say, in effect,
"Regardless of these natural responsibilities we inherit due strictly to biology and culture, the ideal marriage is one where such distinctions are erased - where each partner shares the other's responsibilities to some degree and acts as an equal with the other overall."
I understand completely how hard it is to accept that reading based on all the previous statements by leaders over the years, and the fact that "presiding over" still is used in various quotes, but the actual wording of the Proclamation says just that. In essence, it says that the "ideal" is whatever works best for the individual couple - understanding that the "primary roles" are to provide and nurture.
I view this as similar to the statement, "All men are created equal." First, it is the best they could do in their time (not including women in it); second, it articulated an ideal the society itself wasn't living (slavery) and couldn't live (and still doesn't live). However, just as it was important to have the ideal written into a foundational government document, I think it's important to try to live and accept the ideal of the Proclamation, even though our society (inside and outside the Church) isn't living and can't live it yet.