I'm not sure why the SAA, from 1872, is not considered "modern", while the 1911, originating in the late 1890's, would be. Both have been and are in production, both have been and are reasonably common, both had and have numerous modifications, versions, generations.
Must be that the term "modern" is subjective. Could also be whether in context it is referring to design or application. I think of neither as "modern" firearms, but as "classics". But then, that is highly subjective also.