“Why even bother with baptism then?”
To be baptized in the name of someone, in the Jewish 1st century context, is the same as saying that they are publicly agreeing to receive this person as their lawgiver and teacher. Hence, the Jews were baptized “unto Moses.” Hence the Jews required that converts to Judaism be baptized as a sign of their conversion. Hence all Christians are to be baptized in the name of the Father, Son, and Holy Spirit, as a sign of their new commitment to Christianity. It is not therefore the cause of salvation, but is the result of it, as we see with Cornelius or the Thief on the cross.
You’re not a Jew, and if you already know, why bother with a sign?