Why did god have to incarnate as a human, anyway?

In my belief, God is unique without any son or daughter, without any parent. Original sin is a fiction perhaps. We have fallen to this earth to live and p the time to arrive in another world to continue the way of perfection, all religions have many false things that you have to omit such subjects and get it fruits which is good thought, good speech and good deed from Adam to Abraham, from Mousa to Jesus and to Mohammad, there is not any complicated things, just good thought, good speech and good deed.