The promise to Abraham’s offspring was land, not salvation.
This is not the whole Biblical view. Have you forgotten the book of Hebrews? This will take a few passages.
Hebrews 11:8 By faith Abraham, when called to go to a place he would later receive as his inheritance, obeyed and went, even though he did not know where he was going.
9 By faith he made his home in the promised land like a stranger in a foreign country; he lived in tents, as did Isaac and Jacob, who were heirs with him of the same promise.
10 For he was looking forward to the city with foundations, whose architect and builder is God.
13 All these people were still living by faith when they died.
They did not receive the things promised; they only saw them and welcomed them from a distance, admitting that they were foreigners and strangers on earth.
14 People who say such things show that they are looking for a country of their own.
15 If they had been thinking of the country they had left, they would have had opportunity to return.
16 Instead, they were longing for a better country—
a heavenly one. Therefore God is not ashamed to be called their God, for he has
prepared a city for them.
39 These were all commended for their faith, yet none of them received what had been promised,
40 since God had planned something better for us so that only
together with us would they be made perfect
That something better is the New Heaven and New Earth that is still in the future.
The writer of Hebrews is saying that these people of faith, were not concerned with Earthly land. They knew there was something Heavenly or better that they would not get in their lifetimes.
But a lot of the people saw it as simply Earthly promises.
Jos 21:45 Not a word failed of any good thing which the LORD had spoken to the house of Israel. All came to pass.
But with the coming of the NT, we are shown that these promises also had a spiritual fulfillment. That is what Hebrews is talking about.
Eph 3:8 To me, who am less than the least of all the saints, this grace was given, that I should preach among the Gentiles the unsearchable riches of Christ,
9 and to make all see what is the fellowship of
the mystery,
which from the beginning of the ages has been hidden in God who created all things through Jesus Christ;
10 to the intent that now the manifold wisdom of God might be made known by the church to the principalities and powers in the heavenly places,
3:11 according to
the eternal purpose which He accomplished in Christ Jesus our Lord,
So, whatever promises God made to anybody, Jesus has fulfilled them. I like the New Living Translation on this.
2 Corinthians 1:20 For all of God’s promises have been fulfilled in Christ with a resounding “Yes!” And through Christ, our “Amen” (which means “Yes”) ascends to God for his glory.