Joshua 23:12 Else if ye do in any wise go back, and cleave unto the remnant of these nations, even these that remain among you, and shall make marriages with them, and go in unto them, and they to you:
Their instructions were to destroy the other nations. They were not to live with or among them. The problem would be that they would be tolerant of their gods and false religion. Their children would fall in love with the children of those that didn’t love God.
If this happened then God would stop blessing them. He would leave them to themselves.
They should carefully stay away from other gods or anything that might lead them to worship false gods. They didn’t do this and God did allow them to suffer the consequences of their actions.
Do you realize that God wants your undivided love and attention. He wants you to stay away from anything that might lead you to love another god or to love Him less.
Are you careful to stay away from false gods? Are you careful to stay away from what might lead you away from God?