A number of missives I've authored on science, philosophy, and other topics may be relevant to this review.
Childhood's End is exactly the kind of cerebral science fiction that I enjoy the most. Thinking about the end (of the full book), I think it is one of the more optimistic outcomes of our evolution. That is, it will either be a dystopian nightmare (for us at least) in a worst case scenario and any outcome that leads to something positive will require us to transcend our selves as we currently are. If this even possible (and I think it is in theory), there will be a complete sacrifice of identity, and for some that will be too high a price to pay. Some people may welcome an outcome like what happens in the story and would be happy if that's what happened with humanity eventually. Some would rail against it, as certain individuals. From a scientific perspective, I am not attached to any outcome, but I am interested in figuring out what it is likely to be. In practice, it seems that for a robust complex system to sustain itself (at any scale), a delicate equilibrium between the autonomy of the individual units comprising the system and their collective behaviour appears to exist.
In terms of the movie, the first part was highly engaging and fast paced and set up the story well, but the second and third parts had a lot of filler and while there was a great deal of character development illustrating human virtues and flaws, it really could have been condensed into one in my view. The ending was poignant. The stand out moment was the humanity exhibited by Ricky who is given a rare cure for his affliction but uses it to save Karellen's life. Nothing lasts forever: each individual is around for a cosmic blink of an eye and the entire species not much longer. We are made from star dust, and that is what we will end up as.