Virgin Deterministic Simulation Materialists Vs. Chad Power of Will Spiritualists... (Spoilers, obviously)...
I think this is Alex Garland's meditation on the importance of spirituality and metaphysics...
The header is pretty much the main theme and climax of the movie...
The movie goes to great lengths to show us, super smart, materially accomplished, bElIeVe in ScEinCe (tm) types as the main characters and how they are working on perfecting their understanding of the material world... Lots of time is spent on this from Lily's flashbacks to her father to the other side discussions like her lack of friends and rationalising her distance from her mother during the therapist scene...
I think some of those seemingly "unnecessary" scenes are to show how deracinated and lacking in spirituality these characters are... The series deals with materialists finding a form of faith in order to reckon with their spiritual and emotional pain and emptiness... From the tech founder's guilt over the death of his daughter to Lily recognising how rootless and fake her life was, her only close relationships being spies playing her as an asset and her life being deterministic without will...
At the end, the movie is still tragic with both dying after Lily finds her will to life (very Camus), but at least there is the surface level consolation for the audience that the algorithm computes that the two main characters tech founder & Lily would have found some spiritual closure eventually living in the lie of a simulated multiverse...
Katie (the blonde) is distraught at the end because she conflicted about this... Her inability to handle the implications of Lily's act of will, breaking the system's prediction (into entropic fuzziness), i.e. that her lover is gone and that her time with him was misspent because it was real an not just a deterministic calculation... So she has trouble reconciling her belief in multiverse with such an outcome... She has seen her Deus die, her god die (the machine's predictive ability) and lost her lover at the same time...
It's a much more mature series than Garland's earlier movies, Ex Machina (good movie, cinematic and fun, but still fully materialist) and Annihilation (moody, but not quite philosophical or edifying)...
I think the more materialist geeky viewers may not appreciate what Garland is trying to do here and may be trapped in a Katie like mind trap of trying to "Science the shit out of it (tm)" as Matt Damon's character in the Martian would say...
Hopefully, this will provoke thought... And people will recognise that they aren't in a simulation even if your fate may be written by the gods, you are IRL...