You obviously have no experience in the legal system so your idealistic notions are great for a classroom but utterly fail in real life.
Well, the “real world” results of unfettered, unaccountable prosecutorial discretion has, quite naturally, led to Robert Mueller and his band of merry coup-makers. That’s just what is seen; there are just occasional peeks at the huge numbers and nature of the abuses inflicted upon the American public by out-of-control, unaccountable prosecutors.
I would remind you that the vast majority of these prosecutors are Leftists of one stripe or another. They are also, regardless of their personal politics, generally attempting to “make their bones” with some notorious case or series of cases, so that they can ride their fame up the escalator of political power.
You clearly have no problem with all of this - it is fine and dandy for you. Well, I might be a bit naive as to how the criminal part of our judicial system (note that I did not say, “system of justice” - because it is anything BUT that), but what you are backing is among the most immoral things that one can imagine in a representative republic - unaccountable people. You back nothing less than a usurpation of the authority of the people by skilled bureaucrats. I’ll put my naivete on the scale with what you back - any time.