The British constitution, as we know, is unwritten. It includes a variety of statutes, judicial decisions, charters, and generally-accepted norms established over the centuries.
The Founding Fathers had no choice but to create a written document, given that they did not have hundreds of years of precedents from which to work; accepting the British system as a whole was obviously not a viable option in 1787, given the very different circumstances in the former colonies. Today, however, we do, in fact, have over 200 years of experience. Things have changed, and large gaps have been filled.
I would submit to my readers that ideas such as a depoliticized DOJ, which cannot be found anywhere in the written Constitution, but which are essential to the proper operation of our political system, should be treated not just as “norms” which can be broken without penalty, but as a sort of supplement to the written document that should be treated with considerable deference by all three branches of government.