One could get the impression that the more things change the more they remain the same...
It is illustrative to consider how many of the discontinued systems have been or are being painstakingly rebuilt with new technology. Case in point, the Los Angeles - Long Beach Line is now essentially the LA Metro Blue Line.
Most of LIRR, New Haven and NYC/Conrail commuter service has been preserved with tremendously upgraded equipment on the East Shore, not so much on the West Shore. The PRR commuter service has been substantially preserved, the CNJ and Erie Lackawanna has been partly preserved, while Reading is lost completely at the NJ end, while substantially preserved at the Philadelphia end.
It does call out the chaos that was and to some extent still is, the management of transportation around New York, and there still is not real fix in sight.
Interestingly they are already talking of what came to be BART in 1961. Fascinating to see how reality matches with the vision - or not.
OTOH, there seems to be no mention of any planning for WMATA around Washington DC or anything in LA, presumably because they had not quite been conceived yet and were far in the future.