Existentialism does not require you to deny the existence of God, e.g. see Kierkegaard.  Nietzsche wrote ‘Thus Spoke Zarathustra’, in which a prophet-like figure cryptically explores themes of the Übermensch, the Death of God and the Will to power, leading to diverse interpretations of his message, so he is both embraced and reviled.  An interesting philosopher with some modern views, e.g. we're not a higher species of animal.  We need to consider Original Sin - where does our morality come from?  Is it fixed, or relative and subjective?  Also, we should understand and question our value sets and how to live authentically.  We discussed whether we could live quietly or if we have a responsibility to challenge society.  The French riots of '68 and the countercultural revolution starting in San Francisco were both examples of people collectively finding that they could not live authentically within the structures and values of society at the time.  We now need to consider our current leaders, and also AI and how it will change society. 

John Paul Sartre stated that existence precedes essence.  You are the sum of your experiences, and this is supported by modern neuroscience. There is no objective nature that dictates how we should live, and each person should carve out their own path.  JPS's idea of freedom and his fight for justice for workers still resonates today.