I agree to a point. I don't feel voting beyond local elections has a major effect on much, mostly because the larger and more distant the government figure, the further removed from effects on my life they are, and the more open to corruption they are; however, their choices have massive power as a country and on the world as a whole, and they need to be held responsible for their actions and their actions need to be more in line with what the people desire, and not just of their own countries, but of the entire world, especially those they are going to directly affect through war or economical means.
There are two ways out of that situation that I can reasonably see:
1.) As a people they create new forms of legislators, either in forms of parties (or write-ins or another alternative to parties, preferably) that are held massively accountable by the people through mass demonstration and as threats to the current power who, over the course of years and legislative processes can remove the elements that cause the corruption and pass laws that are untouchable and capable of producing realistic change.
2.) The people abolish our form of our governmental system and salvage the workableparts in the creation of a new form of government that is focused on small communities, possibly smaller than states where the people have a more direct say. I can't say how that would be accomplished or what needs to happen to make it occur because the incidentals are limitless.
Of course, voting should never be compulsory and you certainly should feel a duty to fix things if you plan to leave. I have conflicted issues on that matter as well, as I fully plan to leave at some point as well, cutting all ties entirely to my home country, and yet I still feel that I need to do all that is in my power to change what is currently happening, perhaps out of nostalgia for my home, or a naive hope for a utopia, or just a simple logical progression that my home country has enough power that everything they do will continue to affect me no matter where I live, but I personally will never feel (and this doesn't necessarily apply to you, flagamuffin, but this movement) that if I'm not voting I'm somehow fixing the problem.