I feel like opinions on issues advance incrementally, but once the support is there the issue itself doesn't have to. LGBTQ stuff inched along, until public support hit a majority and then boom, gay marriage is legal. There was a long build-up, and then we were there. On all the issues that could truly help people right now we have the support, but then we either moderate it out of fear of appearing extreme, or we get caught up in small specialty political battles that are morally good but politically dumb. When we eke out victories like this, it convinces leadership they're on the right path because they "won". Voters are mollified because things are "progressing". We're a focus group party and that's why we constantly get trounced by anyone who's authentic, even if they're authentically terrible. The good ideas are on our side but we lack the courage of our convictions. For me personally, I'm moving to the side of taking the pain now of R wins for the longer term goal of moderate Democratic leadership losing its grip so we can found out what the boundaries of the possible actually are rather than what we fear they are. 

I also fully acknowledge I can be wrong. I'm not trying to convince you per se, but to let you know it isn't empty whining from the left but something we (or I at least) have put a lot of thought and calculation in to.