I doubt the aliveness you see is related to the 3-color technique. I would attribute it to the use of large-format plates. Larger formats have invisible grain structure, and the film itself is much thinner as a proportion of the image dimension, which tends to lend the 'aliveness' I think you are seeing. Large formats also encourage use of larger numeric apertures, especially with slow films, so you can often percieve that as more '3 dimensionality' in the image. You can see a similar quality in other large-format color images which are not 3-color separations, e.g.
http://www.shorpy.com/node/1833 . This is a measly 4x5; the russian photographs are probably at least whole-plate size.
It's fairly rare to see large-format color images, because smaller formats were taking over by the time color film was becoming more widely used. By the '70s which you mention, the Nikon F and other Japanese 35mm SLRs were coming out and Kodachrome was in wide use for color photojournalism (National Geographic was a collossal consumer of 35mm Kodachrome). Medium formats like 6x6 were overtaking 4x5 speed graphics well before then, so the bulk of 'old' color photographs are on smaller formats. What's more, early color films were grainier than modern ones.
Of the modern photographers which shoot large formats (like me), I would venture that the great majority shoot black and white. Color film is about 5x as expensive as B&W and rapidly becoming impossible to print. Digital printing works for a lot of people, but if you have to finish on a computer anyway, film loses a big part of its appeal.
Also, remember that digitization did not become practical until the 90's and even now, nobody has incentive to digitize all old color film materials 'just in case', so the color images from the 70s that you see have typically been subject to 20-30 years of fading by the time they are digitized, while these B&W separations are basically unaffected by fading.
