It should affect those born before 1977 as well, but keep in mind that before 1977, there was a pathway for citizenship by descent for any generation with a married Canadian father by registering the child's birth with the Canadian embassy, then there was the delayed registration period from 1977 until 2004 and the special grant of citizenship from 1977 to 2009. If the born-abroad parent did not know about these opportunities for their children or sponsored their children to Canada before the judge's ruling, it's a strong possibility they never intended to reside and establish their 3-year connection to be able to benefit from the ruling now, and any complaint now would solely be based on ignorance of the previous laws when the opportunities were there. To be fair, I did say "mostly, if not all" rather than 'only'.
I think this approach is a bit narrow minded. Many of the 'Lost Canadians' were under the assumption that they had citizenship by virtue of having a parent born in Canada. The 1947 Act featured antiquated laws regarding domicile requirements, registering births in extremely limited time-frames, and laws which freely discriminated on the basis of a person's sex and marital status. The Canadian governmen essentially acknowledged the act's discriminatory practices by restoring citizenship to virtually every Canadian who lost it due to the former act's provisions.
To say someone shouldn't benefit from the new ruling because they didn't follow antiquated laws from the 1940's is quite contradictory. Many Canadians lost (or never had, to begin with) citizenship for years, only to have it restored with the 2009 or 2015 provisions. How could these people be expected to prove three years' residency when they had no legal status in Canada until the past decade? Or sponsor their child when they had no status themselves?
I agree in principe with the 3-year residency requirement, with the stipulation that it only be applicable for those born after 2009. I feel it's necessary for the Canadian government to recognize the citizenship of second generation born abroad children for families whose citizenship was
restored in 2009/2015. These people should be able to claim citizenship by descent without any parental residency requirements. This is the only fair way for the Canadian government to correct its past legislative wrong-doings, as the timeframe between their citizenship restoration and the residency requirement is too short to realistically be justified.