If it is, no one has suggested discarding it.

Practically all religions claiming to be Christian practice something called baptism. If it is a work whose work is it? Who is the actor?

The believer is commanded to submit, "to be baptized" (Acts 2:38). In other words, he is passive.

The promise is "the forgiveness of your sins." That's God's promise and God's work.

No one has done anything to deserve salvation except Jesus Christ, and obeying Him in baptism demonstrates our faith in Him alone as our Savior.

"For it is by grace you have been saved, though faith - and this not from yourselves, it is the gift of God - not by works, so that no one can boast."
Ephesians 2:8,9