They argue that these words could not have been spoken by Jesus. But there is a growing number of scholars, whose research shows that Jesus did use that title of Himself. There are new discoveries helping us better understand Jesus. The main element in Jesus' teaching was His coming suffering and death. Jesus hardly ever foretold his death without also foretelling his resurrection.
Humans simply refuse to assimilate an idea which is strange and alien and objectionable.
They never, in spite of the teaching of Jesus, escaped from that conventional idea. That is why they were quite unprepared for the Cross. And because they had never even looked at the Cross they could not grasp the Resurrection that would follow. Jesus taught them, but they never absorbed His teaching. From the beginning Jesus knew himself as the Messiah whose ultimate triumph and glory were as sure as God is sure.