The meaning of ad astra is the athiests/agnostics wet dream, that we went searching for god/other life and determined we’re it, and that people react in vastly differently ways when they believe that. And that if we want to search for life, to recognize its all around us already on earth. And to let that sink in.
And the father abandoned his son and murdered his crew in the search for the divine alien angels before dying himself. His son lived, returned to earth, to love and life.
It is an atheist twist on the redemptive sacrifice of the son story.