All Scripture is written for a specific people of faith. Though our sacred authors often stress the dignity which faith brings, there are frequent warnings to that specific people that God can accomplish God's will without them, or even with another group of people.
Isaiah gives such a warning. Though he prophesies during the threat of Assyria's 8th century BCE invasion of the Promised Land, he directs most of his oracles not against the invaders, but against the Chosen People.
Often when we seek help for a personal problem, we deflect ownership of the problem by starting our conversation with, "I have a friend who ...." Yahweh employs the same technique, but for a totally different reason. God simply wants the Israelites to first judge this predicament from a human to human perspective. Only later will we find out the identity of the "friend" and the "vineyard."
No matter what the farmer does, the vineyard constantly produces "wild grapes," forcing him to eventually ask the rhetorical question, "What more was there to do for my vineyard that I had not done?" There's just one course of action left: "Take away its hedge, give it to grazing, break through its wall, let it be trampled!"
Though no one in the prophet's original audience could disagree with the owner's decision, it causes them to have second thoughts when he finally identifies the participants in this allegory. "The vineyard of Yahweh is the house of Israel, and the people of Judah are his cherished plant." Obviously Yahweh's not interested in grapes. "He looked for judgment, but see, bloodshed! For justice, but hark, the outcry!"
If the Assyrians are going to conquer Jerusalem, it's not because they have a superior army, but because the city's inhabitants have refused to relate to one another as Yahweh has commanded. Yahweh's justice and judgment will have to be attained without Jewish participation.
Given Jewish familiarity with Isaiah's vineyard story, I've no doubt certain individuals started to squirm when Matthew's Jesus confronts the "chief priests and elders of the people" with the words,"There was a landowner who planted a vineyard."
Jesus' allegory differs significantly from Isaiah's. Unlike the prophet, he zeroes in on the Jewish leaders, not the people. There's also an emphasis on what happens to the landowner's son; an element which Christians would have zeroed in on after Jesus' death and resurrection. But the end result is similar: "The kingdom of God will be taken away from you and given to a people that will produce its fruit."
Though this is an obvious reflection on the unexpected phenomenon of Gentiles as Gentiles joining Christian communities, we must never forget that whenever Matthew points out the failings of Jewish leaders, it's his way of "gently" reminding his fellow Christian leaders of their own foibles.
At this point, he's warning those leaders not to develop the same mindset some of their Jewish predecessors developed, who actually believed they alone controlled God's presence and actions among us. For Jewish/Christians, the recent "Gentile invasion" demonstrated that God is in control of the faith to which they've committed themselves. To fight against this unexpected development would be to fight against God. They're the caretakers of faith, not the owners.
That's why Paul's closing remarks to the Christian community in Philippi are so important. They take us back to the roots of our faith. "Keep on doing what you have learned, received and heard and seen in me."
Unless we want to be "replaced" we must constantly return to the scriptural faith of those who first brought us the faith. It's one way we can be certain we're not spending our lives producing wild grapes.