The reason I maintain my belief, is that Protestantism is not a monolithic belief system. It is an umbrella term for all of the supposed Christian denominations (and “non-denominations”) who dissent from Catholicism in one or more doctrines and beliefs. All of these multifarious congregations favor or lean in the direction of this or that ancient heresy.
I fail to see how Protestantism brought anything new to light. What WAS new, was its surprising ability to shatter Christendom permanently, and steer the cultural development in the West toward the road to infidelity. Protestantism is THE REASON we live in a POST-CHRISTIAN culture.