Of all the metaphors that Jesus uses to explain who he is, Jesus' claim that he is the gate is probably the most under appreciated. Nevertheless, the meaning of the metaphor is abundantly clear. Those religious leaders who do not recognize Jesus as the Son of God are thieves and robbers who do not enter through the gate but come teaching their own doctrines and end up leading the people astray. A true shepherd recognizes Jesus' authority for he is the Word of God, co-eternal with the Father, the Bread of Life, the Good Shepard, and the Light of the world. Finally Jesus plainly states, “I am the way, and the truth, and the life. No one comes to the Father except through me.” Jesus is the Gate. If you want to know the Father and enter the Kingdom of God you must go through him.
The Gospel of John is the greatest theological treatise ever written because it presents the awesome truth of who Jesus is in conjunction with accounts of all those events which prove that Jesus really is who he said he was. If you do not believe it is all true, exactly what are you putting in its place?