The left in the U.S. seemingly has such a poor grasp of coalition oriented politics despite needing exactly that in order to become viable at all as political entities. It's maddening. If people on the left en masse could put their ideals on the back burner long enough (and we're only talking a couple/few election cycles) to force through issues of vote reform and campaign finance reform by working through the Democrats they could spend the rest of their lives voting for people that a) actually represent their values and b) actually have a shot at being elected.
Edit: That time frame may be optimistic, but the point stands. Cooperation/consolidation amongst the genuine left as a voting block/political force, and doing so through the currently actionable political channels, is what it's going to take to get to where we want to go.