This is an instant where the Greek doesn't capture it's original sense in the Hebrew.
In Hebrew 'kabod'(glory) originally meant 'weight'. We see this illustrated in 2 Chron. 5:14,
So that the priests could not stand to minister by reason of the
cloud: for the glory of the LORD had filled the house of God.
In Ex. 33:22, the Lord says to Moses,
And it shall come to pass, while my glory passeth by, that I will
put thee in a clift of the rock, and will cover thee with my hand
while I pass by:
One's 'doxa', no matter how highly regarded, doesn't match the "kabod" of God's Presence. Another word used is 'brightness', or 'splendor", which are certainly attributes of God's glory but don't quite capture the full meaning of the word.
In John 17:5, Jesus says,
And now, O Father, glorify thou me with thine own self with the glory(doxe)
which I had with thee before the world was.
God the Father's opinion of Jesus had never changed,"This is My Beloved Son, with whom I am well pleased(Matt. 3:17)." Therefore, what changed?
Jesus 'traded' His heavenly 'glory' for one of a man. He was sinless, therefore He did not "...fall short of the glory of God". But He traded the 'weight of His Presence' with the Father for the 'glory' of a man, who was made in the image and likeness of God, and made to reflect His glory, which is what we do when we walk "in His Presence" through the power of the Holy Spirit.
Therefore, when we 'exchange',
the glory of the uncorruptible God into an image made like to
corruptible man, and to birds, and fourfooted beasts, and creeping
things Wherefore God also gave them up to uncleanness through the
lusts of their own hearts, to dishonour their own bodies between
themselves: 25 Who changed the truth of God into a lie, and worshipped
and served the creature more than the Creator, who is blessed for
ever. Amen(Rom 1:23-25)
we exchange the 'Presense of God" for the carnal appetites and affections, and false worship-thereby falling "short" of the glory of God.
In summary; the Greek 'doxa' is inadequate in explaining the idea of 'glory'; the Hebrew word "kabod" provides a fuller measure of the truth of the word "glory".