Johns purpose BY Gods will as stated by his fatherThanks, but the OP'er already replied.
He thought John was wasting his time, just like you seem to think.
I can't agree.
And you, my child, will be called a prophet of the Most High;
for you will go on before the Lord to prepare the way for him,
77 to give his people the knowledge of salvation
through the forgiveness of their sins,
78 because of the tender mercy of our God,
by which the rising sun will come to us from heaven
79 to shine on those living in darkness
and in the shadow of death,
to guide our feet into the path of peace.”
I see the baptism of repentance as prep work for the one who can remove sin -Christ Jesus (not a waste of time)