John 14:6 is clearly a divine truth, but in the full context of John 14 there is no statement by Jesus of Himself being some absolute, singular moment in human history leading to an eternal, singular path to God, if you read and consider the full passage.
I mean, it's not a contest here, it's just a group of us bods trying to interpret Divine Revelation, trying to find a path to God with open and humble hearts.
In John 14: 15 - 17 Christ states - “If you love me, keep my commands. 16 And I will ask the Father, and he will give you another advocate to help you and be with you forever— 17 the Spirit of truth. The world cannot accept him, because it neither sees him nor knows him. But you know him, for he lives with you and will be in you.
Christ is making it crystal clear that from heaven He will ask God to send another representative of God on earth and only those who truely know the Christ will accept Him and know Him.
John 14: 25 - 31 “All this I have spoken while still with you. 26 But the Advocate, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you. 27 Peace I leave with you; my peace I give you. I do not give to you as the world gives. Do not let your hearts be troubled and do not be afraid.
28 “You heard me say, ‘I am going away and I am coming back to you.’ If you loved me, you would be glad that I am going to the Father, for the Father is greater than I. 29 I have told you now before it happens, so that when it does happen you will believe. 30 I will not say much more to you, for the prince of this world is coming. He has no hold over me,31 but he comes so that the world may learn that I love the Father and do exactly what my Father has commanded me.
Clearly the Advocate is another being like Christ and because this being and Christ serve the Will of the One God it can be said that this being is Christ returning. The appearance, the body of this being is of little consequence, it's the presence of the Holy Spirit again. The disciples would recognise the Christ in this being.
This explains the going away and coming back. Also the Advocate is not just the Holy Spirit because Christ tells us that He will ask the Father to send another Advocate. As there is only one Holy Spirit the Advocate must be another Messenger like Christ who will be supported by the Holy Spirit as Christ was.
So I'm not sure how the case is closed, there's so much more to consider here as best as I can understand.
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