True, we are all designed by the creator. However, as soon as mankind experienced a fall from perfection he set a plan in motion to reconcile us to himself so that we would finally regain what we had lost. The plan involved a seed, a person who would pay a ransom to deliver from bondage to sin and death and make the eternal life that Adam had lost for us possible.
The first promise of that seed is found in Genesis 3: 15.
That liberator would arrive in the far future at a time chosen by God,
He would arrive via a certain chosen line of humans.
Noah was in that line, Shem, Terah, Abraham, Issac, Jacob, Judah, Jesse, David until during the first century CE Jesus appeared.
During all that time God had used a certain group of humans descended from Shem as an example of mankind's futility in striving to attain salvation via works-that we were still sinners in need of the foretold redeemer mentioned in Genesis 3:15. For that purpose he established an agreement or covenant with them. It brought blessings but along with the blessings a very heavy responsibility to maintain integrity. Because they were still sinners they could NOT perfectly abide by the covenant as specified. So a need to offer animal sacrifices for sin as prophetically symbolic or ritual payment for sin was provided.
In the book of Hebrews Paul explains how god used Israel to provide prophetic symbols that foreshadowed the realities that he had planned for mankind. The high priest foreshadows Jesus, the most Holy of the Tabernacle of temple symbolized heaven, the blood sprinkled on the Ark of the Covenant signified the blood which Jesus would offer on our behave in order to establish a new relationship with all mankind.
So his special attention in reference to Israel was a means for all mankind to attain a blessing. That is why Abraham was told by means of his seed all the nations of the Earth would bless themselves. That is why he reprimanded Peter for striving to prevent the Gentiles from availing themselves of his provision for salvation.