Rome had polluted both the Gospel and the Worship of God by adding to what God had given. In the Gospel, they made the fatal error of putting sanctification (i.e. the process of becoming more righteous) before justification (i.e. the declaration of the verdict 'not guilty'). This effectively turned justification, which biblically is a singular, one-time, ACT, into a PROCESS. And particularly a process that conditioned justification upon a persons righteousness. That is, we must first be sanctified in order to be justified.
But the glorious truth of the Gospel is that God justifies the UNGOLDY. It is "good news" to sinners...not to saints. People who are well do not need a physician...but those who are sick do. Jesus came to seek and save the lost. But Rome had said that salvation is something that you must work out and attain to. The Reformation recovered the free grace of the biblical Gospel of Jesus Christ.
And, as with the Gospel, the Reformation recovered pure worship, meaning, that they took away all the additions that had been added to what God had given. The smells and bells, the new inovations that sought to make the worshipper feel like he or she was in the presence of God, etc. The rule of worship that the Reformers found in Scripture is that we should only do what God commmands. That is, whatever is not commanded is forbidden to be added to our worship.
This was a great relief to those who desired to draw near to God on His terms, but were greatly hindered by Romes props, etc. Jesus called for worship that was in Spirit and Truth, and this is what the Reformation sought to return to.