Probably every believer who has been a believer for any length of time has encountered teaching about the main point or big idea of the following passage:
Matthew 28:18 And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth. 19 Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: 20 Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.
Most have been taught that this passage is “about” the Great Commission that Jesus gave to His apostles. Probably no one has ever thought or said that the main point or big idea of this passage is to teach us about the Holy Spirit.
A careful examination of nearly every sound work on systematic theology or NT theology would likely reveal, however, that this is an important passage for one’s formulating a proper understanding of what the Scripture teaches us about pneumatology. Any person who does not treat what this passage reveals about the Spirit in formulating their theology of the Spirit is a person who does not profit fully from revelation that God has intended him to profit from theologically.
As this brief but clear example shows, it is a faulty approach to hermeneutics and exegesis to insist that the main point/big idea of a passage is all that matters. Truth that God has revealed about a subject in a passage that does not have that subject as its main point or big idea is nonetheless truth that God wants us to profit from fully.