The arc of justice is indeed long, but whether it bends toward justice depends on your perspective. For example, I doubt any of the indigenous people, the few left, of North America, South America, or Tanzania would agree.
It has been centuries since Europeans began pillaging Africa; how many more centuries must pass until that arc bends toward justice for those people?
I'm also not confident change (positive or otherwise) somes from below. Generally, change is initiated by those with, or supported by those, with the biggest club. I'm happy to consider any contradictory examples.