Here is somebody who knows something about Marxism. At 7:29 he says he and some others began publishing a magazine called "Socialism or barbarism" and at 8:19 what he thinks of Marxism since 1964. One can be either a revolutionary of a Marxist; not both at the same time. With subtitles in English.
Interview with Cornelius Castoriadis for the Greek television network ET1, for the show "Paraskinio," 1984 (with English-language subtitles). This documentary describes the life and the work of Cornelius Castoriadis and his turning from Marxism to the ideas of autonomy.