God didn't change, We did.
I look back at the Old Testament and think about how it seems like that God is different than the New Testament God. The Old Testament God seemed to have few qualms with wiping out whole nations but the New Testament Jesus was much more focused on saving each individual.
Our first conclusion on this (I've heard lots of people complain about it) is that God changed. But while going through seminary, my teachers really showed how God worked within the traditions of the existing cultures. And he showed his character through the slight variations in the ways that he did things differently than the gods around them.
And I think there was just a lot of conquering and wiping whole nations out back in the Ancient Near East (ANE). That was just kind of the expectation, I think. So the way that God could show his sovereignty to other nations was to show that he was even master of that game. This is how he showed he loved his people better than the other gods loved their people.
And then as the Roman empire was settling in and personal rights were much more prized, God came in the form of Jesus and met them on these terms. He showed that he was the BEST at caring for the individual. He won at that game as well.
So after pondering this and asking if God changed, I think it's more likely that he stayed the same, but was accommodating our changes.