Once again, chunk, you elide so many other factors to "pin the tale on the donkey". I don't dispute that democracy is in a world of hurt, but this is a condition of entropy that has been happening over decades. There are so many factors - economic, social, demographic, cultural, historical - that have combined to get us here. Hillary Clinton was still in Arkansas when it started, so you can't really blame her. (Besides, she's always been more liberal than her husband.) Americans, and voters in particular, generally only respond to crisis. They just haven't seen it until now. (I've been in a panic abhor the courts since Reagan.) Republicans have had their hair on fire for 70 years, so they're used to it.
I'm with you, my friend, on principles, but you spend so much time on friendly fire at trees, you don't recognize you're in the middle of a forest. If we focus on where we go from here, were much more likely to get there.
For me it's two parts: principles and a sales pitch. Identify the important principles (e.g., family, equality, freedom) and programs to achieve that (tuition relief, healthcare, etc. ), then crafting a message to convince voters to go along. The message will be different for different populations. In urban areas the emphasis has to be on progress and opportunity; in rural areas it has to be on preserving freedoms and security. It's possible to get there with the same programs if the arguments are made right. Rural, urban, white, brown, wealthy and poor all want the same things, they just view them differently. "Security" for a black man means not being shot by cops, but for a white means "keeping my job", for a rich man, it is "keeping my money", for a poor one, " something to eat and a place to sleep".
Universal healthcare, for example, works for everyone. For the poor person, it means health security; for the worker, it makes job security, since it travels; for the farmer, it is one less expense to take away from his profits; for the investor, it makes US goods competitive worldwide; for the elderly, it will make Medicare solvent for the future.
I've tried to make my message clear. To point out the self serving folly of the party leadership and how it's drift from it's historical mission, of supporting the working class to that of being a party of professionals, has led to ruin. The greed heads running the show have sold their soul to finance and technology pimps and hustlers.
Specifically boomers that started this third way neoliberal horror show has led to historic defeat. To this day they will not allow themselves to admit they have politically miscalculated in the extreme.
On the other hand, real left populism is a solution that has deep historic roots of political success in our country. Run on a platform that has broad popular support, win majorities and then do those things you got elected to do. Should be simple but centrist gotta muck that up. Like health care. Make it all means testing with sliding scales and skull shape measuring for something as simple as 'Medicare for All!'. They've created classes of people getting different levels of support that has lead to resentments and complications. Yet the party still wants candidates to steer clear of saying medicare for all...
Finally, stop trying to reel in republican voters by being republican. Start being more like new dealists democrats that were once the majority consensus of the country. As Corbyn has empirically shown us, going populist left works.
What part of that is unclear or shooting at wrong trees? I may reference a political decision or politician's behavior to illustrate my point but didn't realize it was confusing the point.