The promises that God made to the Israelites don't apply to the church. God doesn't give the church victory the same way he gave Israel victory.

I think when you used the word "epistles" you meant the Old Testament books. The epistles are letters that Paul wrote.

The Old Testament is also the word of God but much of it doesn't apply to the church. Such as the laws for the Levitical priesthood. We don't have the right to stone blasphemers or those who violate the Sabbath for example.

I think too many people focus on the Old Testament because they want the blessings that God promised to Israel but didn't promise the church.