Could you tell me what is your understanding of the great commission in Matt. 28 and Mark 16?
For Mar 16, the "baptized" is baptism by the Holy Spirit, not water baptism. It is possible to believe with a man produced belief yet unless one has also been baptized by the Holy Spirit, that belief is not, nor can it be, a true belief, and the person is unsaved. Only a belief that results from the baptism of the Holy Spirit is that with spiritual efficacy, and thereby does it remain, and the person saved.
[Mar 16:16 KJV] 16 He that believeth and is baptized shall be saved; but he that believeth not shall be damned.
For Mat 28:19, the baptizing was part of the teaching, not part of becoming saved. No mention was made in those verses was of salvation.
[Mat 28:19 KJV] 19 Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
What you seem to keep losing sight of is that Jesus alone is the Saviour, man is not. However, you keep returning back to it being a requirement of man's work, not of Christ's. Just a hint, but whenever you reason yourself into a position that requires something of man for his (or anyone's) salvation, you've gone far from the correct gospel track. In all of your posts regarding baptism, you have not once mentioned Jesus as far as I can recall.