Kratos remaining a vengeful murder machine would have cheapened the conclusion of the old series (Ascension notwithstanding). Like, what was he supposed to do from there after killing the whole Greek Pantheon who set him on his path in the first place?

His whole character development was also one of the big draws of the 2018 game, as opposed to the Assassin’s Creed route of “Same God of War but Norse Mythology because why not”.