Martin Luther was frustrated with the Roman Catholic Church for a number of reasons. Let us look at three of the most important of these reasons.
First, and perhaps most importantly, Luther was frustrated with the idea that the rituals and practices of the Church were the way to salvation. Luther came to believe that there was no way that simply following Church rituals could cause someone to deserve salvation. Instead, he came to believe that people could only be saved through their faith and their personal relationship with God.
Second, there was the issue of indulgences. This stemmed in part from Luther’s concern about the idea of being saved by one’s deeds. Luther was even more strongly against the idea that a person could have their sins forgiven based on monetary payments to the Church.
Finally, there was the issue of papal power and the Church hierarchy. Luther came to believe that all people should be able to read about and think about God’s will on their own. They did not need priests and bishops telling them what to believe. Following this line of logic, there was no reason that the pope should be treated as an infallible source of wisdom.
All of these were major reasons why Luther was unhappy with the Roman Catholic Church.
Martin Luther rejected the Catholic Church's practice of selling people "indulgences" to achieve personal salvation. The Catholic Church had abandoned this practice in Germany, but in 1517, the church began to do so again to gather funds to restore St. Peter's in Rome. Instead, Luther believed that salvation could only be achieved by God's grace--a belief he inherited from Augustine. He believed that people should not fear God but should have faith in their ability to be saved.
He also believed that the Catholic Church placed too much power in the hands of the papacy and priesthood to interpret the Bible; instead, he believed that the Bible itself was the authoritative source on religious practice and beliefs. He did not think that only the priests could administer sacraments and preside over the mass; instead, he believed in "the priesthood of all believers," meaning that lay people could administer sacraments and preside over church services.
Luther also thought that priests should be able to be married and that they should not be required to be celibate. In addition, he believed that nuns, priests, and monks should not live separate from others; instead, religious figures should live with people in their community.