The reformers believed that human beings —even saints canonized by the Roman Catholic Church, the popes, and the ecclesiastical hierarchy— are not worthy of the glory that was accorded to them.
That is; that one should not exalt such humans for their good works, but rather praise and give glory to God who is the author and sanctifier of these people and their good works.
Footnote: Part of the teaching of Soli Deo gloria is that all glory is to God alone since salvation is accomplished solely on His will and action.
