If His Kingdom, His Dominion was fully on Earth, wouldn't all sickness, death, pain, sorrow, depression etc, be gone too?
I believe His Kingdom, His Spirit us being poured out on all flesh, Joel 2. But it happens through us partnering with Heaven, we have the keys of the Kingdom. We bind what isn't and release what is in His Authority and Power.
Sharing the gospel of the Kingdom, aligns man into God's will, as sanctification, the soul agrees with Him, then we obey Him in more and more things bringing His Kingdom in greater levels through us and those we disciple.
Jesus said the kingdom of God comes without observation,for they will not say here it is,or there it is,for the kingdom of God is within you,which the saints display the kingdom of God's ways,by the Holy Spirit.
So the kingdom of God in its entirety is not on earth.
During the millennial reign of Christ,God will spare one sixth of the world that fought against Israel,and all that is left of the nations have to go up year after year to worship the LORD,which those are the people that Jesus and the saints rule over.
They took the mark of the beast,but God postponed their judgment until the end of the millennial reign,which then they are judged.
So the kingdom of God is not on earth in its entirety,although it will be Jesus that will rule,and everybody will only recognize Him,but there is still people in the flesh,and at the end of the millennial reign,Satan is loosed from the bottomless pit,and stirs them up to go against the saints,so the millennial reign is not entirely God's kingdom.
The New Jerusalem is a place of only God,and Jesus,the saints,and the angels,where sin has never been,and sin will never be,and rebellion will never rear its ugly head again,and the Bible says that it is a new earth,and a new heaven,and the former earth shall not be remembered,nor come to mind.
That is the kingdom of God in its entirety,for it is completely God's way.
Jesus said thy will be done on earth,as it is in heaven,which that never happens on earth,even during the millennial reign,because of the people in the flesh that took the mark of the beast,but God postponed their judgment,and they go against the saints at the end of the millennial reign and are judged then.
So the kingdom of God is not in its entirety on earth,but can only be in its entirety in the New Jerusalem,for His kingdom would have no rebellion,and only consist of the saints.
But the kingdom of God can display the kingdom of God,but the world will not,and in the millennial reign Jesus rules,and they obey,but there is still people of the flesh that rebelled against God,but God postponed their judgment,and they go against the saints at the end of the reign,so that is not the kingdom of God in its entirety.
Only the New Jerusalem is fully the kingdom come,and the entirety of the kingdom of God.