After more than 5 decades from the release of this Stanley Kubrick’s masterpiece, there’s still much room for analysis and positive criticism. This is largely because the story or screenplay is so ahead of its time.
In the first section, and in the 3 subsequent ones, the monolith is the key to evolution and civilization. This evolution goes on until the protagonist becomes invincible.
I should also point it out that the classical music of the film was a wise selection as it’s created a deep and great ambience in the film. After 2001: A Space Odyssey, this classical music has been the prototype of almost all moving pictures about space.