The symbolic sacrifice that cleansed Isaiah allows him to stand before Jehovah. Isaiah declares that Jehovah called him as His prophet. Jehovah asked who would go, and Isaiah declared that he would.
The message is to tell the children of Israel to see and hear truth. Each of those commands is followed by the sad declaration that Israel is unable to do so. The message is that Israel has not lost its ability to hear or see, indeed, they have not lost the scriptures, through which they hear the word of the Lord. However, they do not correctly interpret what they see and hear in the record of God’s world.
The solution is to shut off their senses, and require that they understand with their hearts—that they be converted and healed. Isaiah has delivered messages of destruction coming to a people who had ceased to correctly follow Jehovah. The solution is to return to faithfulness. They are to shut themselves off to the senses that tempted them with the trappings of the world, and return to the God who knows and dwells in their hearts.