The whole party, and a sizeable chunk of Independents, have shifted left of the average (D) legislator (or, as you said, they have shifted right of the party). But part of the problem with not-so-mythical “Bernie Bros” is that they aren’t interested in some concessions, they want it all or they take their ball and go home. That’s not how a coalition works.
Also: Please don’t feed posters who want to re-hash the 2016 primaries. The 2020 primaries are right around the corner!