Few thoughts:
About me - late 20s black male.
My heart and vote will go to Elizabeth Warren, but I sincerely hope and think she doesn’t win the nomination. Why? She’s amazing on policy but has terrible political instincts. She will lose to Trump. But her ideas will find their way into the 2020 Dem platform.
The winning ticket is Biden / Harris. If we want to beat Trump it’s a slam dunk.
Bernie will never win a Dem primary. Bernie supporters need to get past that idea.
The only serious candidates are Biden, Beto, Mayor Pete, Kamala Harris, and unnamed establishment white male Democrat in the event Biden doesn’t run (think Terry McAuliffe).
EDIT: Terry McAuliffe officially announced he's not running. IMO, that puts Biden's odds at 95% he's in.
EDIT 2 - Prediction:
Bernie retains his 25% base in the primary, while the 4 other serious contenders mention remain relevant through the first few states. Harris has underwhelming support in early states with the exception of California, which causes her support among black voters in the South to tip towards Biden. Mayor Pete has a surprisingly strong showing through the primary. Beto, despite fundraising never catches enough fire and drops out early. That leaves Biden, Sanders, Harris, and Mayor Pete. Harris sees no path to victory, cuts a deal with Biden for an endorsement and promise of VP slot and drops out. Biden runs the table with 40%, eventually climbing towards a solid majority. Bernie refuses to concede without more concessions in the party platform and primary process.
I agree with you but I don't think that should discourage progressives from running a progressive campaign. If you think the population believed Trump felt closer to the center than Clinton, just imagine what her campaign would have been without Bernie consistently pushing her to the left. Does that mean she had a better shot at winning had Bernie not been involved? Maybe. Ultimately, as long as democrats/liberals/progressives/never-Trumpers/etc fall in line when the primary candidate is established, they have a strong chance of winning.You're clearly a newbie to politics. Your arguments are perfectly logical.
However, politics are not logical.
Biden enjoys loyal approval among the Democratic establishment, black voters, and working class white union Democrats. That's the coalition needed to win a Democratic primary.
Liberals do not decide the Democratic primary.'
In fact, even in deep blue states such as New York and California, liberal candidates consistently lose to establishment Democrats. If you're a liberal, your best bet is a center-left Democrat like Kamala Harris or Barack Obama.
The left has a tendency to eat their own, come up with pointless purity tests, and split their votes in a way the right does not. If Biden is the primary candidate, I will vote for him. I won't want to, but I will. The same goes for any other candidate. But if a more progressive candidate wins the primary and loses to Trump, I don't think that's indicative of the narrative that we needed to run someone closer to the center. I feel like we tried that in 2016 and that's what got us Trump. Obama appealed to the exact same working-class white vote that Trump did and yet Clinton's policies were essentially 4 more years of Obama. The American people decided they did not want that (at least from Hillary).