Hi Dlijah23, I certainly will not deny your statement, but will attempt to add to it. Jesus did not complete His teaching with the four gospels; they were but the beginning and those with Him recorded the words and events.
John 1:11 He came unto his own, and his own received him not.
Acts 13:46 Then Paul and Barnabas waxed bold, and said, It was necessary that the word of God should first have been spoken to you: but seeing ye put it from you, and judge yourselves unworthy of everlasting life, lo, we turn to the Gentiles.
Acts 13:47 For so hath the Lord commanded us, saying, I have set thee to be a light of the Gentiles, that thou shouldest be for salvation unto the ends of the earth.
How could this be? Galatians 1:11-12 But I certify you, brethren, that the gospel which was preached of me is not after man. 12 For I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ.
Should we grow further? Colossians 1:25 Whereof I am made a minister, according to the dispensation of God which is given to me for you, to fulfill the word of God. I.e., to fill up or complete the word.
What was the need? There were things not revealed to previous generations. Colossians 1:26 Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints.
My thoughts.