The Church is not the Stone Kingdom itself. This exists separately - and will exist throughout history, according to the promises of God who said as long as the sun, moon and stars endure, Israel will be a nation before Him forever. The early Church was located in the Asia Minor region where all were Israelitish communities. There isn't a single epistle of Paul to those Israelitish communities without a distinct reference to Israel. They would not have understood such allusions unless they were Israel - not 'gentiles'.
Theologians are prone to interpret the word gentiles as being people other than Israel.
The word gentiles isn't in The Bible but they take the word nations , translate it as gentiles then use it for those 'other than Israel'. In truth, Paul was sent far hence unto the gentiles, obviously in context the nations to be known as Spain and probably Britain. He went fulfilling the command 'go not into the way of the other nations but go ye rather to the lost sheep of the House of Israel'. There is a distinction between Israel and heathen. When the word heathen is translated as gentiles, nonsense ensues.