A better way to say it is: God never changes, but the stuff He has to deal with does.
From my post in anothe thread:
There are a few reasons why death was used so often back then. For one, there wasn’t even anything close to an organized society which could have some sort of police force and run things authoritatively. There was in Egypt of course, but these commandments are given to the Jews when they have been freed and are going to have to live on their own out in the wilderness for decades. Also, because they were going to be traveling a lot, there was no way to set up a jail to hold people. All of this put together simply made death the only real way to punish somebody, especially for harsher crimes like murder, because anything less would result in the murderer killing somebody else.
Some may say that banishment would be a better punishment. This might have been true in later years, but in fact that would have been a harsher punishment than death at the time of Exodus. Any man banished would have to wander the desert - all alone, and with no food, and no water. It wasn’t like today or even the middle ages where there were settlements and villages here and there. One could walk hundreds and hundreds of miles before finding even the smallest settlement back then. To sentence a man to that would be no different from sentencing him to a long, painful, tortorus death, so it was a lot more humane to just do it and get it over with. (Moses, of course, survived this, but only because he was God’s chosen prophet and His banishment was part of God’s plan to lead him to Mt. Sinai)
Also, it has been often pointed out that the Jewish people as a whole were like God’s child or children. Parents are obviously more strict with their young children than their older children. God’s people were in their “young” stages. Because of this, he was stricter. When they got “older”, in the time of Christ, God, just like a parent, treated them with more freedom and responsibility. That’s why the Jews could reject God, just like teenagers can reject their parents. (If we continue to anaolgy, we see that God no longer practices very much of any control on people and lets them do all sorts of vile and horrible things people do today, much like parents once their kids grow up and move out can’t say much anymore).
One last point is that, for as much as the Jews were civilized at the time of the Exodus, they were still a relatively primitive people with a lot of uncivility to them. God pretty much had to put such harsh penalties on people to knock some sense into them. He couldn’t have the society develop into one where crime was rampant and nobody cared about anything, so he had to be strict until society was at a point where it kept itself in check without His having to really watch over things.