Compared to what? A quote comes to mind, but I don't recall where it's from: Democracy is a flawed system, but it's the best form of government we've come up with so far.
In a functioning democracy, at least the majority gets to decide. Other forms of government can't even boast that. To say that it's the surest path to oppression is just false. I'm from Germany, I know what I'm talking about.
On some issues democracy will naturally work better than on others. But rich people can't both pay taxes at the same rate as someone on minimum wage and at a higher rate.
But If we assume a base line for what resources people need to survive, taxing the rich at a higher rate than poor people will still hurt them significantly less than taxing poor people at the same rate as the rich will hurt the poor. And no, I have no clue how to further unjumble that sentence.