I'm still firmly in the "Sanders isn't electable" camp. And I'm hoping he's either the candidate, or he gets it taken from him in a brokered convention, and whoever they replace him with is so damaged and suffering from DNC enthusiasm gap that they can't win either.
Honestly, (sadly) for many voters, the talk about Socialism vs. Capitalism is just too damn highbrow. If you focus on that alone, I guarantee you're over thinking it. I'm convinced that the optics, mannerisms, and speech of a candidate mean far more to the "middle" and "undecideds" than policy and party. And it's been that way since Kennedy beat Nixon after the first televised debates. And in elections where candidate optics and style are close, like 2000 Bush v. Gore, folksy "aw shucks" Bush, vs. Newscaster-like Gore, the election is close. And where it's far apart, like Reagan vs. Carter '80, or Reagan vs. Mondale '84, the election results are further apart. School-marm'ish Bush Sr. managed to beat out Dukakis because he looked like a bobblehead in that (in)famous tank photo op. Then it flipped, Bill Clinton's Saxophone vs. George Bush won the day. Obama's skill as an orator (when on teleprompter) beat out McCain. I think Hillary's shrill cold and inauthentic imperious style was very different, but evenly matched with Trump's bombast, and you see it in the popular vote, and Trump "only" managed to win on an Electoral College path through the northern Rustbelt on cultural issues.
Other than Ford v. Carter who was arguably irreparably damaged by Nixon's fallout, it can be argued that for the past 50-60 years, the more photogenic candidate and the one who was more likable in their manner of speech has won. Trump is insufferably bombastic, but his delivery is light years beyond Bernie's quavery "you kids get outta my yard" old man mannerisms.
It matters less in the primaries because the lack of undecideds, squishy middle, and low information voters mean that's a much purer ideological contest than the general election is, despite the general election being more polarized. And that's why you've got this plurality of "I'm a Democrat but I can't vote for a Socialist"-voters opposed to Bernie, they just can't decide to get behind one other candidate. It's still important to note that when it comes to an enthusiasm gap for Democrats while Bernie is either winning contests or polling 1st or 2nd place, he's never come close to a majority. (And Trump in some states like NH has doubled or tripled incumbent president primary turnout over what Clinton, Bush, and Obama got, and beat everyone since Reagan...)
Assuming that the delegate process is still ultimately under their thumb, and Bernie doesn't come into Milwaukee with an insurmountable majority of delegates... I think it might be coming down to the DNC deciding how it is they want to lose. They're trying to decide if the down-ballot damage in House and Senate races with a Bernie candidacy is worth the trouncing they'll get. And the hope is, that can be used as a club to beat the DNC's Left wing into submission for a generation. (See how badly you hurt us? Now shut up, and go away vote for the establishment Democrats like you are told to!) And they probably want to save someone like Buttigieg on the bench for 2024, when the 8 year presidency party flip momentum is stronger. OTOH, they may want to run someone less damaging, but still likely to lose, hoping to retain control of the House.