Now put on your thinking cap and think instead of blindly accepting what someone says.
Isa 7:14 says what will happen is a sign. A young girl giving birth to a son,would be an every day event in Jerusalem. That could not qualify as a sign from God.
You are not "thinking" at all, omega2xx.
Did you bother to read THE WHOLE OF CHAPTER 7 at all, omega2xx?!
The sign was given to Ahaz by Isaiah, when they (kingdom of Judah) was at war with Rezin of Aram and Pekah of Israel:
Isaiah 7:1 said:
1 In the reign of Ahaz son of Jotham son of Uzziah, king of Judah, King Rezin of Aram and King Pekah son of Remaliah of Israel marched upon Jerusalem to attack it; but they were not able to attack it.
What the gospel quoted (Matthew 1:23) is only small part of the original sign (Isaiah 7:14-25 and 8:3-18, and just the beginning of the sign. You are only talking about partial sign, not the whole sign.
The Isaiah 7:14 is just the beginning of the sign, but the sign doesn't end in this chapter until the very last verse - 7:25.
However the child's involvement in the sign - Immanuel - doesn't depends on just with his birth, but the next 3 verse which relate to downfall of the two kings (Rezin and Pekah) at the hand of King of Assyria:
Isaiah 7:14-17 said:
14 Assuredly, my Lord will give you a sign of His own accord! Look, the young woman is with child and about to give birth to a son. Let her name him Immanuel. 15 (By the time he learns to reject the bad and choose the good, people will be feeding on curds and honey.) 16 For before the lad knows to reject the bad and choose the good, the ground whose two kings you dread shall be abandoned. 17 The L ORD will cause to come upon you and your people and your ancestral house such days as never have come since Ephraim turned away from Judah—that selfsame king of Assyria!
The "he" in 7:15 and the "lad" in 7:16 are Immanuel. When Immanuel reached the age that he know how to choose good from bad, and that the people of Judah will be reduced to eating curds and honey, the king of Assyria (7:16-17) will invade both Aram and Israel, the land or ground of "two kings" (Rezin and Pekah).
The passage may have begun with 7:14, the rest of the sign (7:15-17) revealed the development of when the sign will be fulfilled.
The rest of the sign (7:18-25) involved more about the king of Assyria than about the child.
The king of Assyria which is revealed to be Tiglath–pileser III (reign 745 - 727 BCE) in 2 Kings 15:29 and 2 Kings 16:7, contemporary of Pekah and Ahaz.
The sign involved more than just Immanuel's birth. And the fulfilment of the sign would happen sooner than Matthew and you claiming to be. The sign 7:14-17 showed that Immanuel is merely signpost of what will happen in Ahaz's reign, which had nothing to do with virgin birth and messiah.
Isaiah 8, plus the sign given in verses 3 - 4, is also relate to Ahaz, Rezin, Pekah and the king of Assyria. Except that the passage (8:3-4) revealed that the woman in 7:14 is Isaiah's wife and the son Immanuel is his son Maher-shalal-hash-baz.
Isaiah 8:3-4 said:
3 I was intimate with the prophetess, and she conceived and bore a son; and the L ORD said to me, “Name him Maher-shalal-hash-baz. 4 For before the boy learns to call ‘Father’ and ‘Mother,’ the wealth of Damascus and the spoils of Samaria, -and the delights of Rezin and of the son of Remaliah, d shall be carried off before the king of Assyria.”
And 8:3-4 is just small part of the sign about the king of Assyria getting involved in the war.
Isaiah 8:5-8 said:
5 The Lord spoke to me again: 6 Because this people has refused the waters of Shiloah that flow gently, and melt in fear before Rezin and the son of Remaliah; 7 therefore, the Lord is bringing up against it the mighty flood waters of the River, the king of Assyria and all his glory; it will rise above all its channels and overflow all its banks; 8 it will sweep on into Judah as a flood, and, pouring over, it will reach up to the neck; and its outspread wings will fill the breadth of your land, O Immanuel.
Immanuel is mentioned again (8:8), in relation to his war, more sign about Immanuel and king of Assyria.
The only person
"blindly accepting what someone says" is you omega2xx, who have been blindly following the gospel author, you cannot even think for yourself. You are more ignorant than I thought.