The ultimate conclusion at least for me is that it is our innate nature, including our flaws that make us worthy. The simple aspects that make up human nature (the ones discarded as archaic or low by the Overmind and its followers) that ultimately make us worthy. That is love, and human connection, the simple and pure aspects of humanity. Honor and Self Sacrifice, Duty, Love, Friendship, Loyalty, Bravery, Humility. These things are what we need to overcome an indifferent universe, not by being gods, larger and stronger than it, but by being able to survive, able to maintain the delicate flame of life and civilization
In archangel, it is simple humanity, simple human emotions, human love, human virtue that is able to create a turncoat within the Overmind's forces, create an Archangel and savior of mankind.
Likewise in Wilderspace, it is the bonds of humanity, love and community, fellowship, etc, these are what help us to unite and survive extinction and overcome the Revenant Overmind