"Kingdom" doctrine is a big deal with a lot of ministries today. But is it all being taught well? Or are Christian people being given extreme expectations that end up leaving them broken and disappointed?
The Old Testament predicts a glorious time when God's presence will visibly re-establish itself upon the earth. Messiah will conquer God's enemies, and idolatry will stop. Man will beat his swords into plowshares, and will learn war no more. This bundle of Biblical hopes eventually became known as the "kingdom of God." These was the Jewish expectations when Jesus came, and it explains a lot of the puzzlement and frustration with Him that the people felt. Christ often had to point out that there were many other kingdom prophecies about Messiah suffering and dying (such as Isaiah 53) that the people either were ignoring or had never learned.
Jesus in Matthew 13 show Him re-defining the kingdom. Jesus says that the kingdom would manifest now through preaching, and there would be varied responses to the preaching (13:1-23). The kingdom would have true and false believers co-existing alongside each other, like plants in a field or fish in the sea (24-30, 47-50). God's kingdom would start out tiny and grow up to be very large (31-32). It would penetrate society like yeast working though dough (33). People would stumble across God's kingdom almost by accident (44-46).
The Old Testament predicted God's kingdom will come down to the earth from heaven suddenly, visibly, catastrophically, by force, and enacted by the Messiah personally. It would judge the whole world, and condemn all the unbelievers. Jesus said the kingdom will come through the earth slowly, invisibly, progressively, through secondary workers, by means of teaching, preaching, and persuasion. The kingdom would forbear with unbelievers, and allow false and the true disciples to co-exist for a time.
Christ never said the OT prophecies were untrue, or that they wouldn't happen. He revealed new information -- mysteries hidden before He said them -- that this is a new time and mode for God's kingdom. These are the ways that the kingdom of God is manifesting in these times, as well as through the indwelling of the Holy Spirit, and miracles of the Spirit.
The kingdom of God is not fully realized now. That idea leads to untrue expectations and quick disappointment about what to expect from God in this world. But the kingdom of God is not absent from this world, either. The Christian Church, the general assembly of the First-Born, is the avatar of Christ's kingdom in the earth. Through us the kingdom of God is affecting the current age.