There are many ways that humans can be oppressed; the means of oppression are threats to survival, poverty, threats to freedom and corruption and these threats in all societies are present, but as societies become more prosperous the risk of each threat changes.
When humans are starving, they worry about survival; when humans are poor they desire to become wealthier; when humans are wealthy they desire to be free; when humans are free they desire to be governed by governments that serve them, not by governments that serve themselves. That is the natural progression of human thought and development.
It should be unsurprising that in Brazil more than a million people are actively demonstrating against corruption. There are now fewer starving people in Brazil, there is more wealth and the people are free, but they are oppressed by corruption.
It is part of the human condition that we are never really satisfied by the existing state of affairs we must strive for perfection, in health, well-being, freedom and in government.