I don't think it was or would be smugness, with regard to the platform component of electability at least, to recycle success. If anything (and again, I'm only speculating from a campaign strategist's point of view, not an ideologue's), it would be much more pragmatic than a 'clean slate' approach to platform construction would have been in 2016, when inheriting a share of the popularity banked by your own party's two-term president. Hillary established a left/right track in the Senate that was comparable to or even slightly left of Obama, and her campaign generally didn't stray very far from that in the 2016 election. So with a similar overall ideological blueprint to Obama/Biden but ultimately saddled with a candidate we (and polling) agree was less likable than Obama, Democrats won the popular vote in 2016. Again, I'm not advocating for what I think is best for the country or even the Democratic party; I'm just saying that there's probably a fairly strong contingent inside their machine (strategists, rainmakers, etc) who see A] the electoral landscape as not being direly changed from 2016, B] their loss in that election as more the fault of the candidate than the platform, and C] therefore little incentive to reinvent the Democratic wheel with more spokes made of socialism, particularly when the consequences of a failed experiment are viewed as direly as they are. Then again, in a year's time a portrait of Karl Marx might poll above 55% in a hypothetical head-to-head vs. Trump and by going with Biden, Dems might miss a once-in-a-generation chance to leap to the left and remake the landscape of American politics... ... or consign themselves to irrelevancy for the first half of the coming decade, for that matter.