Heidegger's ontology attempts to reconcile scientific Being with Dasein by appealing to Kierkegaard's theory of the Self. The problem here is that Kierkegaard doesn't give a damn about science. He goes out of his way to denigrate systematic approaches such as Hegel's, and he would have most likely scoffed at Heidegger's approach as well. And yet Heidegger finds much to like in Kierkegaard's "phenomenology" of Dasein, and stealthily appropriates much of it. Wychogrod's analysis is highly technical, but it successfully describes the difficulties that Heidegger runs into when he does this, and why this approach dooms his mission. Kierkegaard's theory of the self harbors an irreconcilable contradiction which is simply incommensurable with science. What is remarkable is how well this contradiction comports with our experience of Dasein.
Some aspects of Heidegger's project became more clear in comparison. Not that it appears less confused and futile. Both thinkers want to carve of out a domain for the divine to persist, in light of progress of science, and defy the consequent determinism. Kierkegaard's attempt is far more honest and relatable.