We Jews have had this text in our Scriptures for millennia. Not only do we not accept that Jesus of Nazareth is the Messiah, we have not ever read this to think it foretells the incarnation of God. The text isn't even viewed as messianic.
While I totally reject the teaching of Jehovah's Witnesses, even its anti-Trinitarian stance (though I don't subscribe to the Trinity, of course), these texts never literally say the child is "the Messiah," and the use of the word "God" in a name is very common in Hebrew. "Michael," for instance, is literally "Who is like God?" The Witnesses take advantage of such views to promote their very odd take on Christology.
Jews see these verses as applying to Hezekiah. He is given a name at his birth at Isaiah 9:5 which in Hebrew reads: Pele-joez-el-gibbor-abi-ad-sar-shalom. The "el" part is the word "God." In Hebrew it means: "The Mighty God is planning grace; The Eternal Father, a peaceable ruler." It is describing Hezekiah as being the graceful, peaceable ruler planned by the Mighty God, the Eternal Father. Jews don't read it as if it is saying that the child is God.
However, the central view of Christianity is that God came in the Person of Jesus Christ. While not immediate from Scripture, the idea predates the canonization of the Bible (at least the New Testament). The teaching that Jesus is not God come as Epiphany creates a foreign, problematic form of Christianity. Christian tradition is that God became man so man could share in God's divine nature. The Watchtower view is a poor cousin form of Christianity by comparison.