The key point, however, is that the Church teaches one thing, while her members are quite able to believe what they want to believe and live as they want because they have the freedom of their wills. This is why we have Catholics that do these things. Their own ways of life are not the beliefs of the Church. Once someone is baptized as Catholic, they remain Catholic. The bad people, yes, even there were many immoral popes, were bad Catholics and their actions were scandalous for the Church, but the uniformity of the Church comes from the Church's own beliefs, not the practices of its individual members.
There were quite a many popes throughout the Church's history that probably were some of the worst human beings of their time in terms of behavior. The Church is holy, not necessarily all her people who fall short of the glory of God big time. As terrible as they may have been, they never made an erroneous statement of faith binding upon all Catholics to believe that contradicted anything the Church had already taught and believed.
As for Joan of Arc, what we often forget is that we had a political conflict between France and England. The French and the English were both vastly Catholic nations, yet were political enemies. The citizens of these kingdoms were fiercely patriotic, including the clergy. So, we have the French clergy supporting Joan of Arc and these visions they believe to be a holy sign, and the English clergy saying she is possessed by demons. So, when the English got ahold of this French soldier that she was, they let their patriotism get far ahead of their mercy. She was tried by an inquisitional court by the English clergy, and found guilty. Now, what was supposed to happen was that she would be kept under the guard of nuns as was the custom for female prisoners of her status. What happened instead, is the English government stepped in and put her in a secular prison where she was abused by English male guards who worked for the state. She was later executed by the English. This was because she had lead the French army against England. It was a political matter first, and the politicians freely used religion to justify their actions (just like many do today). She was made a saint because she died a holy death at the hands of an enemy who used religion for political gain against the teaching of the Church. The Church did not have her executed. The English did. The Church had planned for her to spend her days under the watch of nuns, and the English intervened to have her put to death to avenge the insulting losses suffered under her French troops.
Again, the Church's doctrines are not subject to popular opinion. There are 1 billion Catholics worldwide, but there is only one Catholic church. The Church teaches what she teaches and will not change the faith. Any one of those 1 billion have the ability to profess Catholicism with their tongues and betray it with their thoughts and actions. It's free will.