Then the seventh angel sounded; and there were loud voices in heaven, saying, "The kingdom of the world has become the kingdom of our Lord and of His Christ; and He will reign forever and ever. Rev 11:15
... saying. We give You thanks, O Lord God, the Almighty, who are and who were, because You have taken Your great power and have begun to reign. Rev 11:17
Notice verse 18: And the nations were enraged, and Your wrath came, and the time came for the dead to be judged ...
All after the seventh trumpet, when the earth becomes the kingdom of God and He begins to reign upon it. That does not fit with "it will always be a spiritual kingdom". Although I agree, right now it is just that. Remember, just as the apostles saw Jesus leave the earth He will return in the same way (Acts 1:11).