In the abstract, it might be tempting to imagine that irreducible complexity simply requires multiple simultaneous mutations - that evolution might be far chancier than we thought, but still possible. Such an appeal to brute luck can never be refuted... Luck is metaphysical speculation; scientific explanations invoke causes.
Is the conclusion that the universe was designed - and that the design extends deeply into life - science, philosophy, religion, or what? In a sense it hardly matters. By far the most important question is not what category we place it in, but whether a conclusion is true. A true philosophical or religious conclusion is no less true than a true scientific one. Although universities might divide their faculty and courses into academic categories, reality is not obliged to respect such boundaries.