In America, who you vote in has very little effect on public policy, and by very little I mean a near zero/statically insignificant amount (unless you're part of the top 10% of income earners):
http://fightthefuture.org/videos/does-voting-make-a-differen...
Counterpoint: My friends and associates do amazing things. Marriage equality, marijuana legalization, DREAM Act, etc, etc. I (a yeoman) also do what I can.
Maybe think of politics, society, culture like thermodynamics:
Organization requires continuous effort, to mitigate entropy.
I'm not saying people shouldn't be active. Groups like The Anti-Corruption Act (https://www.youtube.com/watch?v=lhe286ky-9A) are doing a lot, not to mention the group that pushed Maine's ranked voting amendment.
But the vote itself is not very useful. There are other forms of activism that are more worthwhile; those that seek to slowly and fundamentally change the system. Focusing on the left right paradigm will ultimately lead people to being angry at two parties that are essentially the same.
Liberal supreme court judges do not materialize out of thin air, do they?