From Alister McGrath, “Reformation Thought: An Introduction” (Kindle Locations 423-440). Wiley. Kindle Edition; pgs 2-3 in the print edition:
By the beginning of the sixteenth century it was obvious that the church in western Europe was in urgent need of reform. The popular cry for “reform in head and members” both summed up the problem and pointed to a possible solution. It seemed to many that the lifeblood of the church had ceased to flow through its veins.
The church legal system was badly in need of overhaul, and ecclesiastical bureaucracy had become notoriously inefficient and corrupt. The morals of the clergy were often lax and a source of scandal to their congregations. Clergy, even at the highest level, were frequently absent from their parishes. In Germany, it is reported that only one parish in 14 had its pastor in residence. The Frenchman Antoine du Prat, archbishop of Sens, turned up for only one service at his cathedral: moreover, his presence and role at this service was somewhat passive, since it was his funeral.
Most higher ecclesiastical posts were secured through dubious means, generally relying upon the family connections or the political or financial status of the candidates rather than their spiritual qualities. Thus Duke Amadeus VIII of Savoy secured the appointment of his son to the senior position of bishop of Geneva in 1451; if anyone had misgivings about the fact that the new bishop had never been ordained and was only eight years of age, they were wise enough to keep quiet about them.
Pope Alexander VI, a member of the Borgia family (famous for its lethal dinner parties), secured his election to the papacy in 1492 despite having several mistresses and seven children, largely because he bought the papacy outright over the heads of his nearest rivals.
Niccolò Machiavelli put the loose morals of late Renaissance Italy down to the poor example set by the church and its clergy. For many, the cry for reform was a plea for the administrative, moral, and legal reformation of the church: abuses and immorality must be eliminated; the pope must become less preoccupied with worldly affairs; the clergy must be properly educated; and the administration of the church must be simplified and purged of corruption.
For others, the most pressing need concerned the spirituality of the church. There was an urgent need to recapture the vitality and freshness of the Christian faith.