Since the time of Constantine, when the RCC took hold politically,
This never happened.
it continually changed its doctrine, heeding to the "doctrines of men" rather than the will of the Father.
This general narrative isn't historically accurate. Or more accurately it is wildly oversimplified to the point of being wrong.
For one, Constantine can be credited with only about two major things:
1) The legalization of Christianity with the Edict of Toleration which ended State-sponsored persecution against Christians.
2) Invited bishops from across the Roman Empire to gather to the city of Nicea to address the controversy surrounding Arianism.
Beyond this, Constantine became a major patron sponsoring the building of churches and the publishing of Bibles, passed laws which granted to Christian clergy the same rights which had been afforded to pagan priests (e.g. Christian clergy were exempt from serving in the Roman military).
Now, do we see a growing closeness between the Christian Church and Roman imperial power? The answer is yes, by the time we get to Theodosius I, Christianity had went from legal to official religion of the Roman Empire, and the emperor in essence came to be viewed as the defender of the Church, a role which would continue to shape Roman, and later Byzantine, policy, politics, and the complicated relationships between church and state.
With the fall of the western Roman Empire to the migrating Germanic tribes, and many of those tribes having previously converted to Arianism through Arian missionaries, the circumstances became ever more complicated. While many of the Germanic tribes would convert to orthodox Christianity, others held out longer (such as the Visigoths who eventually established a kingdom in former Roman Hispania). In the absence of Roman political leadership in Western Europe, the power vacuum was filled mostly with Germanic tribes and nations, with the Ostrogoths and Lombards in Italy, the Vandals in North Africa, the Visigoths in Spain, the Franks in Gaul and Germania, etc. Even Roman Britain would eventually be invaded by waves of Angles, Saxons, and Jutes, who would eventually form the Anglo-Saxon kingdoms (which later were unified as England).
In this power vacuum and in the turbulence of the collapse of the western Roman Empire there was basically only the bishop of Rome left to provide some semblance of stability. But then there emerged a power struggle between the Germanic nations and the Byzantine Empire, eventually under Justinian Rome and portions of the Italian peninsula did come back into Roman (Byzantine) possession, and Justinian assured the bishop of Rome safety. But this would change in time leading to Rome again being under pressure from invaders. But here the Frankish king Pepin came to Rome's aid, which created a bond between the Kingdom of the Franks and the bishop of Rome, indeed Pepin granted the bishop of Rome a parcel of territory around Rome, thus making the bishop of Rome an land-owning sovereign--this small territory would come be known as the Papal States.
With the death of Pepin, Pepin granted his kingdom to his two sons in the hopes that they would jointly rule. That didn't happen, and eventually a struggle between Pepins sons Charles and Carloman ensued, with Charles taking full control of the Frankish kingdom. Charles, like his father, would come to the bishop of Rome's aid, which resulted in the bishop of Rome crowning Charles "Emperor of the Romans", thus signifying a recognition that Charles was the legitimate successor to the Western Roman Empire. This Charles became known as "the Great", and hence his Latin name
Carolus Magnus, or as we know it from the French, Charlemagne. With the crowning of Charlemagne emperor in of the Romans in the West, the bishop of Rome put the future of the Western Church into the hands of western European powers for centuries to come; whereas the Eastern Church (which was still in Byzantine lands) looked to the Byzantine Emperor (the Emperor of the Eastern Roman Empire). The Byzantine Emperor did not recognize the validity of the "emperor" in the West. And so, even more political upheaval.
This is the situation going in Western Europe in the late middle ages. Yes, the bishop of Rome did gain political power in time, but not from Constantine, but through Pepin and succeeding European powers; yes the bishop of Rome's ecclesiastical authority increased in the centuries of this period, eventually leading to a strong centralized church based in Rome with the bishop of Rome evolving into what we would eventually call the papacy.
But this is complicated history. No, the "Roman Catholic Church" did not come to power from Constantine, nor did the Church in the west have much power at all for most of the middle ages. The Church was, mostly, at the whim of warring and rival political powers, and seeking to find stability by recognizing strong kings. And all of these various historical forces eventually resulting in the conditions of Western Europe that we see in the late middle ages and the Renaissance, and more instability coming from within the Church by the Papal Schism during the Avignon Papacy, the controversies surrounding the Conciliarists and their opponents. And these are the things we see after the Great Schism of the 11th century between East and West, the crusades which ultimately soured relations with Byzantium and the Christian East even further with the sacking of Constantinople during the 4th Crusade, the creation of the Latin kingdoms in the east, the return of the Byzantine Empire, the bad attempts at reconciliation at Florence, the fall of Constantinople later to the Ottomans. Etc, and so on and so forth.
Eventually providing fertile soil for something massive to happen when a devout German monk and professor of theology decided he wanted to have a university debate over indulgences being sold in Saxony in 1517.
-CryptoLutheran