You entitled to your opinion, I believe the Man Christ Jesus as Mediator was begotten before the world began. He was both Firstborn/begotten of all Creation Col 1:15 and of the Resurrection of the Dead Col 1:18Since they wrote these books and letters often decades after Jesus was already taken to heaven, they were just speaking in past tense about something that already happened using their updated knowledge of Jesus to refer to him. Acts 13:33 is clear about the prophecy of Jesus being begotten being fulfilled at his resurrection.
So if Jesus was already begotten before this, then how does Acts 13:33 make sense any other way?
15 Who is the image of the invisible God, the firstborn of every creature:
18 And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence.