"To my fascination, I’ve seen a couple articles floating around which essentially misinterpret the song by forcing their own eschatological presuppositions and “poo poo” its traditional characterization as a Christmas song. Those of us who understand it in the sense of being a celebration of the first advent are then issued a slap on the wrist along with a disapproving tsk tsk.
If we fail to understand that postmillennialism was the dominant eschatology in the 18th century during which this hymn was written, and that author Isaac Watts himself was an ardent postmillennialist, one could see how it could be assumed that Christ’s second coming was Watt’s intent behind the Christmas hymn “Joy to the World” and not his first coming.
But first, simply notice the tense of the song is not future. Watts could have easily written, “Joy to the world the Lord will come” or “the Savior will reign” or “He will rule the world”, but he didn’t. The fact that he chose not to, fits perfectly with his inaugurated postmillennial eschatology. The song is intentionally written to highlight and celebrate the present, earth redeeming imperatives of Christ’s first advent. The Old Testament picture we are given by the prophets of Christ’s first appearing is that it was a cosmic event, forever altering the course of history."
If you are a Premillennialist, you are going to have a problem with a lot of old hymns.