Though the writer of the book of Hebrews is not clear, the message it deliver is clear and resounding; Christ is supreme over everything the Old testament stood on.
The book was written to a Jewish-Christians who considering converting back to Judaism until the persecution by the emperor subsided. The message of the book of Hebrews is; Jesus is greater than the angels, than; Moses, the giver of the law. Than Joshua, Aaron and Abraham.
The book of Hebrews was written during the period when the emperor, Nero, persecuted and killed Christians everywhere he could find them. He favoured Judaism over Christianity and so the writer was encouraging the believers, especially those who had converted from Judaism to Christianity, not to consider going back to Judaism just to escape persecution.
In chapter one, we see Jesus, the Son, radiates and expresses the glory and character of God. In other words, Jesus is the one we see whenever we look for God.
"The Son radiates God's own glory and expresses the very character of God, and he sustains everything by the mighty power of his command. When he had cleansed us from our sins, he sat down in the place of honour at the eight hand of the majestic God in heaven." Hebrews 1:3 NLT.
Outside Jesus, you can't see or know the Father.
Secondly, the Son is the one who holds everything in the universe together, they are sustained by his very command;
Thank you Father for giving us Jesus. Halleluyah!