That's part of my point. The left isn't enthused for the primaries because we rarely have a passionate fighter who's willing to actually stand up for the policies we want. We just go with whoever wins because generally, they're all the same candidate, and generally they just serve up platitudes and bullshit which doesn't inspire anyone.
That is really not what I see. Historically candidates who are more left of center do better in primaries because their supporters tend to be more involved with the process and issues. This is why McGovern was nominated in 1972 and part of the reason he lost so big. Bernie in 2016 was another classic case in point. In what was essentially a 2 person race he ran strongly against the establishment candidate Clinton. I remember when he announced his run in an interview with Racheal Maddow and said he did not expect to win, but his goal was to serve notice that the left was not to be ignored and to move Hillary further from being a center right candidate to more of a center left candidate. He did that. However in 2020 many of his ideas had morphed into planks in various campaigns and in a divided filed he quickly was diminished in vote totals.
Extreme candidates always do better in the primaries - look at the Tea Party movement, any anti-war movement and the pattern is always there.
The problem comes when the general election arrives and most voters, however unhappy they might be are not willing to go all in on dramatic (i'm not even saying 'radical' here) change. They want incremental improvements. Yes, everyone wants universal healthcare - but no one wants to be honest about paying for it. Warren tried. She was leading the pack when she released her plan to pay for Medicare-for-all. Her plan was a bit of a stretch - a lot of things had to go exactly her way - but it was not unrealistic. Bernie never really laid out specifics and it killed him with the middle voters who needed to support him to win. The attacks against his ideas went largely unanswered and that is fatal in almost all arguments. He did not broaden his base of trust.
We on the left of center have a hard time educating people to the idea that change is good because the conversation has for decades been dummied down - mainly by the GOP and now more so by social media. There is still among many people an idea that if something is on TV, or God help us, the internet, it must be true. Public education, long the whipping boy of conservative and their long game has produced several generations now of idiots who cannot think or understand what their interests actually are and move towards them.
Wally has laid out one aspect of the problems we face - the pretty girl at a bar is not too far off - but the problems we face are extremely deep and embedded in the system to the point it is our DNA.