In a western democracy, you can, at least in theory, freely criticize those in power without fear of retribution, but also without any hope of your criticism changing anything. It's just a pressure release valve. When criticism starts taking a form that might force change, the mask and the gloves come off, as you can see in the violence against protesters once protests reach a critical mass.
You can't force change, sure, but that doesn't mean you can't be part of it. Individuals can and do join political parties and become influential within them. Political parties win elections and ultimately set policy which can start to change things.
None of those things happen quickly, and most people don't succeed in their attempt to do it. That doesn't mean it's not possible. I'd argue that it's a feature of the system that the system makes it hard to change course - it averages out the extremes.