Complex sentence: The Orthodox Church is decentralised, having no central authority, earthly head or a single Bishop in a leadership role, having synodical system canonically, is significantly distinguished from the hierarchically organised Catholic Church whose doctorine is the papal supremacy.
Split into simpler sentences: The Orthodox Church is decentralised, having no central authority, earthly head or a single Bishop in a leadership role. Thus, the Orthodox Church uses a synodical system canonically, which is significantly different from the hierarchically organised Catholic Church that follows the doctrine of papal supremacy.