Symbolism in Season 4 Finale "Final Grades"

After finishing the show a few weeks back, this episode has stood out in my mind more than the rest, the final scene in particular.

When Donut pulls up in front of Namond's new home to show off his ride, he then drives off, running a stop sign. The camera lingers on this intersection, showing a father and child crossing where they could have been hit just moments before.

What message was the show trying to communicate here? Up to this point we see a few characters who are let down by the system;

Carcetti is bogged down by bureaucracy and budgets. He knows he's trying to do the right thing but the system is full of hurdles put in place by the mismanagement and greed from characters like Clay Davis and Burrell.

Colvin walks out of the presentation discussing the findings of the school experiment. He doesn't see the value in research because the children they were studying are pretty much as screwed as they were before.

Carver spent the past few episodes fighting as hard as he could for Randy only for him to end up in foster care anyway. We see him screaming in his car as he comes to grips with the fact that he couldn't help him, even when he was just trying to do the right thing.

These scenes communicate to me a sense of helplessness and futility. No matter how hard these characters try to do good, "the game is rigged."

Finishing on the stop sign, I feel as if the show is essentially telling us that "The world is full of assholes that only care about themselves, and this is what we're up against." Random violence and greed are ingrained in society at all levels and we can't do anything about it.

edit: https://youtu.be/DOgAQbwKqzA