Existentialism is uncomfortably close to essentialism, and in that takes the wrong approach to understanding life

Camus's allegory of life using the Myth of Sisyphus is incomplete because Camus asks the wrong question. He considers 'why' to lead to a revelation and not the 'how' of existence. For him the absurdity of existence lies in the 'why' of it, and the considerations of the 'what' are used to guide the argument towards answering the ultimate 'why' question. In that it is too reductive, it focuses too much on the essence of life, the meaning of it, the one archstone that completes the large edifice of argument.

Instead if he'd asked the 'what' question, he'd have understood that there is no absurdity in existence. Existence is a functional property of 'us', to exist is to 'be' all the atoms and subsystems in one's body. The 'purpose' of human existence is nonsensical, as much as the purpose of an atom's existence is. Instead if we understand what it is that makes us, and how it works, he'd have started much revealing arguments. "What are we?" and "How are we (how do we work)" are questions that can answer questions raised by Camus, and existentialists much better than the approach they themselves took.