I love the dinosaur sequence because it displays a truly incredible thought that I hadn't considered before. If any one creature in your entire evolutionary lineage had been killed or died before they could procreate along the way you simply would not exist. All of your life and your very comprehension of existence would cease to be before it even started. How the velociraptor decides not to kill the injured dinosaur for seemingly no reason, allowing not only that creature to live but the countless others that stem from that dinosaur, is as baffling and maddening an idea present in the film as any other if you think about it. It's such a simple moment but it's ramifications are remarkable.
Malick is a great philosophical director in that he makes you consider ostensibly massive ideas you hadn't before, just how that dinosaur sequence had me realise and contemplate the absurdly delicate balance of life and death over billions of years that allowed my existence. He is exploring the deepest thoughts that plague the human mind on both a philosophical or macro level and a personal or micro level through self-analysis of his familial relations and life experience. For example his relationship with his father and how it affected him, which I found to be particularly cutting in it's relatable presentation, is something that the film concludes to be so integral in the man one might become. Sean Penn is a successful architect but memories of his life and his upbringing have him feeling utterly lost, it's genuinely amazing how Malick depicts this so perfectly purely through beautiful imagery, ingenious editing and disjointed inner monologues.
He is always trying to convey our human perception of this life we didn't ask for and the incalculable facets of it that we constantly question. It's funny to me when people label him and this film pretentious because his complete and utter honesty in exploring these deep and fundamental questions about life and it's personal meaning through the medium of film is the least pretentious a director can get I think. This movie is a modern masterpiece as many others here have stated and its stature will only grow in our hearts and minds as time goes on.