What was the main thesis of M. Luther, from which the whole program of the reform of the Church flowed?

The main thesis is that the Pope does not have the right to ascribe to himself the remission of human sins, and also to charge a fee for it. Luther’s main idea was that each person is saved only by his sincere faith in God and does not need an intermediary in the form of the Church. Priests as a special group of people are not needed, so they should be abolished.