Yeah I get that. But that would imply that the early scriptures are giving us an inacurate view of who God really is. Or else it would imply that what is held to be an accurate view of God is only based on our perception and culture.
The Old Testament does several things,
God is revealing to is what we need to know, and only what we need to know , for our salvation. ( God, for instance, doesnt dicuss the physics of black holes)
God is preparing the Old Testament peoples, and us , for the coming of Jesus, His Incarnation.
The relationship between God and His people is being written as it grows, The Jews as the chosen of God, and their interactions with God , and their realisation that God is all , power and mercy. Covenants are made, God never breaks them, people do. God will never break a covenant.
The Old Testament, and the New Testament are filled with instances where we and they are taught there is only one God. All other pagan , gentile gods are demons.
God is also mercy in the Old Testament, as much as He is bringing the end of wickedness. One example is Cain being cast out, but being given protection . Another is the Noah flood where those not wicked are saved, another with Nineveh, Jonah is sent to announce its destruction, the entire city listens and repents, God does not destroy it and has a great discussion wih Jonah on caring about His entire creation