Or start actually getting involved in the political process and primary any Republican supporting this.

I get that the system seems to be fixed to lock people out, but why is this always only said by people who think voting constitutes the maximum level of participation in democracy?

The Leftists understand this far better than most of the people on this site do. You don't change things by just pushing a button every four years, you change it by going to every meeting, delegating, making a stink about every stupid thing they do, fundraise for radical candidates, use elections as opportunites to push your message, etc.