Between communities' ideas of what the police are for and will do, and the reality of both, there is a big giant gap.

At present, there is no way to close that gap, or even to get communities' expectations communicated to the police and legal apparatus. Not that the police would be responsive if they could, because they are underresourced for their roles as they define them, through choosing not to do some of what people expect of them.

I am not talking about all police, but making a generalization about departments based on my own and family members experiences over time. Roles have changed. Expectations, until people have occasion to interract with police, have not.

I find it appalling how many people are wrongfully convicted, and how hard it is to introduce evidence to prove the innocence of the wrongfully convicted

Seems to me the facts show us the system is not just:

There have been 310 post-conviction DNA exonerations in the United States.
[snip]

• 18 of the 310 people exonerated through DNA served time on death row. Another 16 were charged with capital crimes but not sentenced to death.
[snip]

Races of the 310 exonerees:

193 African Americans
93 Caucasians
22 Latinos
2 Asian American
http://www.innocenceproject.org/Content/DNA_Exonerations_Nationwide.php

Let's not forget the scumbag judge in PA who was taking bribes to send kids to detention centers.

That's just the tip of the unjust iceberg.

American justice favors those that can afford great lawyers and to the even bigger guys that can buy judges.

except for all the rest, to steal a line from Churchill. I think you are spot on about money and access to differing levels of quality counsel. Take the OJ trial. He didn't get off because he was black, he got off because he was wealthy and could hire enough lawyers to raise a reasonable doubt. The racist detective didn't help the prosecution's case but the jury would never have heard about that if OJ had been a poor man with a court appointed attorney. Until 50 years or so ago one didn't even have the right to a court appointed attorney. If you couldn't afford a lawyer you just didn't have one. But overall I think the system works pretty well.

Better than anybody else has figured out? Yeah, probably.

one should then reach, is that one has a constant obligation to watch what happens and try to make such difference as one can

Its all about pacification, pseudo-empowerment and greasing of the wheels of commerce. "Justice" is a notion to keep the irrelevant peasants happy, while the system steamrolls them collectively and forces them into virtual servitude (or literal, for those stuck in the justice system's prisons)

Which makes it basically unjust.