I've seen this sentiment expressed over and over here this week, and it's really frustrating to read.
Want to stop people speeding on a road? Issue tickets. In some sense, that's not fair -- people still do it and get away with it, why single out one person? But having a non-zero possibility of a negative consequence is a net disincentive to the behavior. Even if it's enforced somewhat randomly.
Hypothetically: let's suppose that our goal is to stop "the system" of prosecutors threatening multiple felonies against citizens for behavior that most other citizens do not consider worthy of a consequence as serious as jail time/felony conviction. Let us also assume that some prosecutors do this to get prestige/promotions. If there are well known examples of positive consequences, and no examples of negative consequences, then the incentives for our hypothetical prosecutor are pretty clear.
It seems fairly obvious that if Ortiz and Heynmann face seriously negative career consequences, it changes the cost/benefit calculation for other prosecutors, even those whose main concern is career advancement.
There aren't many ways to hold public officials accountable besides public outcry.
I do agree that the root problem is the human psyche. We have all kinds of bugs/heuristics (depending on how you look at it) for social behavior. These lead to group behaviors that us abstract thinkers find frustrating. Unfortunately, this isn't going to get fixed until 20+ years, and that's if you're on the optimistic side about transhumanism. So in the meantime we have to use the tools (and brains) that we have.