Today, in the words of John the Baptist quoting the prophet, God Himself speaks to us.  And God invites us to prepare the way for the Kingdom established by the Messiah in the power of the Holy Spirit. There is the work for Christ's followers, who have been baptized, not with water, but with the Holy Spirit.
Isaiah the Prophet spoke to the people of Israel who were then in exile that their nation will one day be the place where God's glory shines forth (Isaiah 40: 1-5).  That was the message for a people with no hope.