The point that Jesus is making when he says that there are some standing here who will not die before they see the Son of Man coming in his kingdom is that there are some to whom he is speaking who will not die before the prophecy of Daniel 7 is fulfilled, in other words, before Jesus receives the kingdom from his Father.
Jesus received the Kingdom upon his ascension. There are many scriptural proofs, highlighting that Jesus will continue to reign through his Cross, until he destroys all power, dominion and authority. When he comes back, he would have fulfilled this and also defeated the last enemy death, Satan and hell. At this point he becomes subject to the Father (1 Corinthians 15:23-28).
In addition, we see the declaration.....
13“In my vision at night I looked, and there before me was one like a son of man, coming with the clouds of heaven. He approached the Ancient of Days and was led into his presence.
14He was given authority, glory and sovereign power; all nations and peoples of every language worshiped him. His dominion is an everlasting dominion that will not pass away, and his kingdom is one that will never be destroyed. (Daniel 7:13-14)
"In the time of those kings, the God of heaven will set up a kingdom that will never be destroyed, nor will it be left to another people. It will crush all those kingdoms and bring them to an end, but it will itself endure forever. (Daniel 2:44)
Again.....it comes down to where Jesus sat when he ascended up on high......
"'The Lord said to my Lord: "Sit at my right hand until I put your enemies under your feet."' (Matthew 22:44)
Again........
But Stephen, full of the Holy Spirit, looked up to heaven and saw the glory of God, and Jesus standing at the right hand of God. (Acts 7:55)
So it was fulfilled, that those who stood listening to Jesus, were alive to witness the ushering in of the Son into his Kingdom in Heaven, where he went to prepare a place for his bride. (John 14:2-3)
Even the High Priest was told that he too will not taste death, until he witnesses the event, where the Son will ascend to sit on th right hand of the Father and to reign from his Heavenly Kingdom, in his Father's house,
64“You have said so,” Jesus replied. “But I say to all of you: From now on you will see the Son of Man sitting at the right hand of the Mighty One and coming on the clouds of heaven.” Matthew 26:64)
when Jesus speaks of the “coming of the Son of Man,” he is purposefully alluding to
Daniel 7:13–14
For sure, but you are missing the evidence that's point to him being given the Kingdom at his ascension.