The New Hollywood era is generally considered to begin with 1967’s Bonnie and Clyde, following the accidental but hugely successful US mainstream release of the 1966 British film Blow Up. Kubrick’s career straddles the eras, so he doesn’t belong to the young crop of new directors, e.g. Scorsese, Mallick, Coppola, Spielberg, that defined the movement, but I think it’s fair to say Kubrick’s output from the late 60s onward, to include 2001, absolutely leveraged the creative freedom studios were relinquishing to directors and writers.