What is the problem with mainstream Christianity according to this teaching?
The problem is that much of mainstream Christianity stops at the elementary teachings and never moves into the deeper things of Scripture. As a result, believers lack understanding of the deep doctrines that Paul was privileged by the Holy Spirit to give in his letters to believers.
Les explains that Paul's letters are always written only to believers, not to the unsaved world. He notes that a new person totally untaught in Scripture does not have to know all the deep doctrinal things to be saved; in fact, such people are the easiest to work with. But once a person becomes a child of God, God expects that believer to learn, grow, and get a graphic understanding of all that God has done on their behalf. Les says the problem with so much of mainstream Christianity is that they may have the elementaries, but they have never gone into the deeper things. Consequently, they have no understanding of the deep doctrines that Paul is now privileged by the work of the Holy Spirit to give to us in his letters. Paul writes to us believers, and he says, that's not you.