The problem with reading the Pentateuch as portraying God in a primitive way and then reading the NT as though it portrayed God in some more “sophisticated” way is that it isn’t really true. God is a God of both justice and mercy, of both holiness and compassion, of both purity and love in both testaments, Old and New. God is at least equally passionate in both collections of books.
The old caricature of the God of the OT being a God of wrath, and the God of the NT being a God of love is just that—a caricature. Nor is Christ portrayed in the NT as somehow less interested in justice and righteousness than Yahweh in the OT.
Witherington, Ben, III. Torah Old and New: Exegesis, Intertextuality, and Hermeneutics. Minneapolis, MN: Fortress Press, 2018.