The Democratic party is a diverse, wide coalition where the Republican party is a homogeneous, narrow coalition. Different Democrats win different districts. Let the voters decide. This election we're running all of the above, centrists in very right States (manchin), liberals in right leaning States (Beto, Abrahms), liberals in purple states (Gillum), etc.
The Dems gave up on the undercard during Obama's years, and now we have to rebuild. Let's see who gets elected this year before saying we need to do X because of 2016.