Democrats not representing so many of us leads to people becoming disillusioned and not voting. Having to choose a lesser evil instead of an actual good sucks. So Democrats are to blame for not representing their constituents, and voters are to blame for not voting for the least bad result out of practicality.
Thing is, the party did this for three elections running. People don't like being railroaded, particularly with the contempt and condescension that centrists can't help but express.