Well, why should a party do anything for you if you don't vote?
Do you think sitting it out is going to change things? They'll suddenly care about your issues because...?
It's not an accident that both parties are attentive to Medicare and Social Security. It's because they know if they don't, they'll pay a price with seniors.
If you follow me here on Twitter, you may have noticed me explaining that they have actually changed a little over time, shifting radically on key issues -- solely because they thought they could get the votes of more voters that way.
Sitting out the political process doesn't hurt them one bit. In fact, it makes their life *easier* because they have fewer voters to reckon with.
Show up at party meetings, make your voice heard, do the grunt work, run for local office, all that.
At mid-century, conservatives were largely on the outs of the political process. The felt ignored too. But they went to work and effectively took control of the Republican Party over a few decades. Now they set its agenda.
If enough people like you make your voices heard, then they'll have to listen, if only because it'll be in their *own* self-interest to take you and your interests seriously.