Ya you're right, Luke 3:21 says," Now when all the people were baptized, it came to pass, that Jesus also being baptized, and praying, the heaven was opened"...
I can just picture that, John baptizing Jesus.. I john baptized thee Jesus in the name of yourself.
And I can picture Jesus praying, by the way who was he praying to?.. Thank you heavenly Father for allowing Me to be baptized in My own name.
Did you get the message? We are baptized in the name of Jesus for the remission of sins. Who is Jesus? He is the Word. Where did the Word come from? Itself? And the word was with God, "which is the Father Son and HS", and the Word Was God.
When you get a deeper understanding of the Word, you'll see that baptizing in the name of the Father, and of (meaning the name of) the Son, and OF (meaning the name of) the HS is proper to say name in the singular.
God is a mystery, but did you get His (notice the Word His is singular) message? Now how can we say "His" ( meaning God) when God is three persons in one? Because we can.
You need to realize that the bible is a generalization of terms to relay and focus on a central message which is, the Word which is always all three persons. They are never separate, Jesus said," I and My Father are ONE. So be careful how you criticize the Word.