Ad Astra is your typical brooding near-future sci-fi film similar to Interstellar, Gravity, First Man (well not near-future at all, but still, brooding), Blade Runner as of late These movies are then in turn inspired from 2001: A Space Odyssey.
In films, being typical is usually not an advantage to the eyes of some people, mostly critics. Overall, the Ad Astra fell short due to lackluster supporting roles, messy story-line, cheap thrills (space monkeys) and off the mark pacing.
The center of the film is McBride, a young upcoming astronaut and the son of probably the most successful one. Peppered throughout the film are internal narrations of McBride's thoughts akin to a literary fiction. His thoughts revolves around loneliness and to an extent, the movie's central theme: loneliness in space, of missing a love one, of not having a father growing up, of billions of miles of nothingness, of man being alone in the universe. Add to that is we only see McBride's perspective throughout the film further selling the point of being lonely even when surrounded by people. As an expense, the supporting roles is fairly lacking, we don't ever hear the voice of his wife and just snapshots of memory.
It has the recipe for a great film, the ingredients just didn't work.