One of my favourite passages in the Bible was the gospel reading for Sunday, Mark 1:14-20.
Pithy, direct, active. Jesus preaches (a very short sermon!) and calls without preamble or ceremony his first disciples.
In the brief message is everything Jesus will do and say (all about the kingdom of God).
In the call is the call to all who hear the message: Follow Jesus.
The "me" in "Follow me" is illuminating. Jesus has no ego yet calls people to follow him alone, even giving up, as the fishermen do, everything that has been their life and livelihood.
Connecting the "me" with the "time is fulfilled" and have a very Jesus-centred kingdom.
When Jesus comes, the kingdom has come.
What Jesus does is the kingdom breaking into the world as Jesus takes charge of the world.
Jesus is the king.
The kingdom of God is the kingdom of Jesus.
Followers of Jesus join with Jesus in kingdom of Jesus work.
As servants of Jesus we obey Jesus' rule and thus do the things which assist the growth of the kingdom.
As servants of Jesus we may be tempted to think the kingdom's future growth depends on us and is exclusive to our good obedience to the king.
No, the kingdom is greater than us and God in Jesus continues to do kingdom work in the world with servants we may know nothing of (and who may not realise they are serving the kingdom!).
While we can never know all that God is doing in the world - providence - we can be confident, because of passages such as Mark 1:14-20, that God is doing those things in the world which fit with what we see of Jesus' words and deeds in the gospels, including those things which Jesus-centred disciples say and do in obedience to Jesus.
So, yes, the kingdom is greater than the church but never less than the church.
The church, in the long run and for the most part, because of promises of God concerning the Spirit-led, Spirit-gifted body of Christ, will visibly demonstrate the kingdom in the world today.
But errors in teaching and in behaviour do occur in the life of the church and thus the church can frustrate the growth of the kingdom.
If we want to not be frustrating then we do well to read and re-read and respond and re-respond to Mark 1:14-20.