That's it. Voting is something you can do right now. It's not perfect, it's not going to solve everything overnight, but it's a step. It's an opportunity to do at least something.
Imagine the following scenario : you spent four hours today cleaning the flat spotless, hoovered under every furniture, scrubbing the wall tiles in the kitchen, everything. Of course you missed/forgot some stuff here and there, but you gave it your best. Your flatmate was lounging on the sofa the whole time, eating chips and watching TV. In the evening he insists you listen to him for three hours lecturing you on how clean flats should be in an ideal world.
Yeah, because that's how it feels to listen to political opinions from non-voters. If you don't do the absolutely minimal possible effort to get involved then you have no say in how things go, period.