One of the most specific attributes of the Lord is His uniqueness in creation, His uniqueness in kingship, and His uniqueness in management.
By attributing a son to Almighty God, it would imply sharing divine attributes with that son , as a son typically inherits his father's traits.
Thus, the son would share in the management of affairs, the creation of beings, the sovereignty of the kingdom and the disposition of ownership.
So if Almighty God had s son:
•God would not have been sovereign over everything as the son shares in divinity.
• God would not be One and Unique.
• God would not be the First and the Last.
• God would not be the sole All-Powerful over everything.
•God would not be the sole All-Knowing of everything.

You say that Jesus is God because he existed before the creation of the universe.
But what about Solomon who said in Proverbs [8:22-30]
"I was with God from eternity, before the creation of the world. I was always by His side, rejoicing in His presence, and I was with Him as a creator."
So by this logic Solomon would be more deserving of divinity than Jesus.
And what about Jeremiah to whom God said
"Before I formed you in the womb, I knew you, and before you were born, I consecrated you." (Jeremiah 1:4-5)
If existing before birth makes someone divine, then why is this not applied to Solomon and Jeremiah as well