Jeremiah 33:22 I will make the descendants of David my servant and the Levites who minister before me as countless as the stars in the sky and as measureless as the sand on the seashore.
When God promised to give Abraham more descendants than he could count it was not a promise that Abraham would be able to see happen during his lifetime, but something that he would have to trust would come to pass.
God is not always going to deliver things to our front doors so that we see everything the way we want to; sometimes He delivers stuff that we only get to hear about well after we think it was overdue.
God knows the perfect time for things because He is not limited by time like we are. We need to rely fully on God and not impose our own limits on what He can do!