Isaiah was a prophet from God. This means that as a prophet, he was speaking the words of God to God's people. Same type of thing that a Pastor should be doing every Sunday to his flock when he preaches and teaches from a given Bible text (God’s still living breathing active words). Yes, Isaiah as a prophet, speaking for God, was giving some future information for the people to hear. But 75% of what Isaiah was speaking for God was dealing with the people that were (not) listening then and there. And why was Isaiah speaking the words of God for the people to (not) digest then and there? Isaiah was calling God’s people back to God. The people of God around Isaiah had forgotten God and were living more and more each day like the world around them. Do you feel peer pressure many times to live like the world around you? Do you feel your church has become more like the world and culture around it? Has the church as a whole gotten more and more like the fallen sinful world it lives in, rather than the Savior of it? I would answer yes to all 3 questions. So, Isaiah and his call for God’s people to not live like the world is very relevant for the church today.
A second reason Isaiah is still relevant today is because the main topic in the book is repentance of the people of God. Isaiah is calling God’s people to repent and turn back to Him. Because if they do not repent and turn, a coming judgement will happen. Isaiah is sure that the coming judgement will take place because God tells him in chapter 6 that the people will not listen. But Isaiah still calls for repentance and foretells God’s coming judgement. But Isaiah also shows in his prophecy that there will be a restoration and future hope in the coming Immanuel for the remnant that God saves who do repent and turn from their wicked ways after the judgment of God. This call is still the same for God’s people today. Which shows that Isaiah’s call to repentance and future hope is very important for the people of God to hear, right now, in the lives they live in daily.