Whilst one can certainly see points of comparison with Kubrick's film, albeit on a much smaller budget, Silent Running has its own charms thanks (given that these matters touch you) to the sincerity of its ecological message well embodied by Bruce Dern as an astronautical flowerchild and the simple way that it is presented. Dern’s performance is, to say the least, exaggerated but in many ways he needs to be to justify his in extremis behaviour - Lowell is a man who is passionate about his values, no tame conformist, a precusor to the eco-warrior.
If the early stages of the film show Trumball’s lack of directorial experience and often look like they are in spoof territory like John Carpenter’s Dark Star (1974), once Lowell is left alone with only his little robot companions, Huey and Dewey, the film acquires a strangely poignant quality that made me think of Dorothy in the Land of Oz (unfortunately instead we get two songs by hippie diva, Joan Baez), a quality that goes a long way to explaining the film’s cult status.
Probably not a film for straight sci-fi fans but if you enjoyed the Lost In Space television series this will probably give you some pleasure.
FYI: The script was co-written by Michael (then calling himself Mike) Cimino with Deric Washburn who would work with him on The Deer Hunter (1978) and TV writer Steven (then calling himself Steve) Bochco.