I don't believe that christianity was meant for the 'gentiles' anyway and I think that is part of its mess, it makes no sense to me that god would change his mind, and it makes less sense, that god would now be a son and a spirit, so what can I say?.. That is just my view on the matter...
I understand that this is what you believe. It may even be what is taught in Islam. But it is not what is actually taught in the Bible.
You see, though many Muslims like to refer to the verse where Jesus says, "I was sent only to the lost sheep of Israel." (Matthew 15:24), that is not the end of the story. It is true that Jesus was sent to Israel, for he came as the Jewish Messiah. But it not true that his followers were to be similarly so restricted.
1) First, even Jesus himself ministered to more than just the people of Israel. In this very story itself, Jesus goes on to minister to the Canaanite woman:
Matthew 15
21Leaving that place, Jesus withdrew to the region of Tyre and Sidon. 22A Canaanite woman from that vicinity came to him, crying out, "Lord, Son of David, have mercy on me! My daughter is suffering terribly from demon-possession."
23Jesus did not answer a word. So his disciples came to him and urged him, "Send her away, for she keeps crying out after us."
24He answered, "I was sent only to the lost sheep of Israel."
25The woman came and knelt before him. "Lord, help me!" she said.
26He replied, "It is not right to take the children's bread and toss it to their dogs."
27"Yes, Lord," she said, "but even the dogs eat the crumbs that fall from their masters' table."
28Then Jesus answered, "Woman, you have great faith! Your request is granted." And her daughter was healed from that very hour.
Please note, that this entire event takes place while Jesus is in "the region of Tyre and Sidon." These are Phoenician cities along the coast north of (i.e., outside of) Israel. And the conclusion of the story shows Jesus granting the request of this Canaanite (i.e., non-Jewish) woman. There are many other stories of Jesus engaged in ministry outside of Israel and with Gentiles, but to use this single verse to declare that Jesus is exlcusively ministering to the Jews and brings a message for them alone is to glaring miss the context that the whole event takes place outside of Israel and in the midst of Jesus ministering to a non-Jew.
2) Second, Jesus specifically directs his disciples to be in ministry and making disciples among not just Jews but all people:
Matthew 28
18Then Jesus came to them and said, "All authority in heaven and on earth has been given to me. 19Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age."
Acts 1
7He [Jesus] said to them [the disciples]: "It is not for you to know the times or dates the Father has set by his own authority. 8But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth."
Thus, even from an understanding that Jesus generally (though not exclusively) restricted his ministry and message to that of the Jews, he does not so do with his disciples. Rather, he expressly sends them out -- to make disciples of all nations (the Greek behind that term refers to all ethnicities). Jesus tells his disciples that are to be his witness, taking his message, not only to the Jewish world, but globally.
3) I believe you err when you see this as God changing his mind. For Israel's role was never to be God's only people. They were chosen for a purpose, and God makes that clear to them in the words of the prophet Isaiah:
Isaiah 51:4
"Listen to me, my people; hear me, my nation: The law will go out from me; my justice will become a light to the nations.
Isaiah 60:3
Nations will come to your light, and kings to the brightness of your dawn.
The Jews were to live in covenant with God and become a beacon to other peoples so that they too would be drawn into relationship with the one God. The nation of Israel may have failed with that respect, the the Jewish Messiah, Jesus, did not. And, to this very day, he continues to "draw
all men" (John 12:32), not just Jews but also non-Jews (i.e., Gentiles), to himself.