It's not a story about people. It's about marvelling at vast expanses of time and space . . . .
I find that a puzzling defense, given that it has characters and a sembalance of a story involving them. If it's all about marvling at time and space, make a damn 2-hour VFX reel and leave it at that.
It's not just an special effects show. There
is a story, but it's not about individual characters the way that conventional stories are. It's vast saga, spanning hundreds of thousands of years, about the evolution of humanity as directed by some unknowable alien intelligence. Humanity as a species is the protagonist.
Dave Bowman or Heywood Floyd are no more the subjects of the movie than the apemen at the beginning of the film, or the astronauts who stumble onto the monolith on the moon. It's science fiction in the tradition of Olaf Stapledon, involving the sweep of history, instead of a story about specific individuals confronting some sort of crisis.