From various passages in Isaiah, you can assemble a list of signs that Messiah would perform.
61 The Spirit of the Sovereign Lord is on me,
because the Lord has anointed me
to proclaim good news to the poor. He has sent me to bind up the brokenhearted,
to proclaim freedom for the captives
and release from darkness for the prisoners, 2 to proclaim the year of the Lord’s favor
and the day of vengeance of our God, to comfort all who mourn, 3 and provide for those who grieve in Zion (Isaiah 61, NIV)
In that day the deaf will hear the words of the scroll,
and out of gloom and darkness
the eyes of the blind will see. (Isaiah 29:18)
John the Baptist knew this, and so he asked Jesus if he was the messiah, because the list of things Jesus had performed was not the complete list he expected.
18 John’s disciples told him about all these things. Calling two of
them, 19 he sent them to the Lord to ask, “Are you the one who is to
come, or should we expect someone else?”
20 When the men came to Jesus, they said, “John the Baptist sent us to
you to ask, ‘Are you the one who is to come, or should we expect
21 At that very time Jesus cured many who had diseases, sicknesses and
evil spirits, and gave sight to many who were blind. 22 So he replied
to the messengers, “Go back and report to John what you have seen and
heard: The blind receive sight, the lame walk, those who have leprosy
are cleansed, the deaf hear, the dead are raised, and the good news is
proclaimed to the poor. 23 Blessed is anyone who does not stumble on
account of me.” (Luke 7, NIV)
If you compare the lists, one very important sign was missing, important to John because it concerned him:
The freeing of the captives. This includes all who are unjustly imprisoned and all slaves, like John himself.
The freeing of the captives was a sign that Jesus left for the church to fulfill. Healings were a personal blessing to individuals. Setting prisoners free requires a change to government. What did Jesus say about that?
6 Then they gathered around him and asked him, “Lord, are you at this
time going to restore the kingdom to Israel?”
7 He said to them: “It is not for you to know the times or dates the
Father has set by his own authority. 8 But you will receive power when
the Holy Spirit comes on you; and you will be my witnesses in
Jerusalem, and in all Judea and Samaria, and to the ends of the
earth.” (Acts 1)
Fundamental, night-and-day change to government by Messiah will occur at the second coming. Slow improvements in government and the accumulation of civil rights and justice has been the work of the church, slowly learning this by the Holy Spirit and making many mistakes along the way.