Even outside of the left/right dynamic Biden's cabinet choices are a big sign of the decay within the party. The patronage networks are full up of people who aren't competent or popular as the failures keep piling up from administration to administration. There also aren't enough seats to go around as the dems population base is completely disproportionate to the amount of territory they control. It's going ratchet up the pressure for the bottom of the party to cannibalize the top, but not necessarily along ideological lines as even the moderates aren't going to have a career path unless they can make people like John Kerry fuck off.