She was the best candidate at the time.

So good she dropped out before any votes for the nomination happened in 2020 and had no steam in her home state?

So good that she failed educating the registered voter base she was running, instead of Biden?

So good she wanted to keep Trump's promises of a strong military and border?

if the issue was the message and framing, then keep the candidate and fix the framing and message.

The problem wasn't how she said anything, it never is. The only lesson Dems ever take when they get trounced at the polls is that they need to target their messaging better. There's never any self-crit about the possibility they might need to change their policies. They just assume that an electorate who doesn't want corporate-friendly status quo politics is simply wrong, and needs to be propagandized more convincingly. E.g., 2/3 of the US population agree rich businesses and individuals need to be taxed more. But the Dems assessment seems to be that the majority of the country is wrong on that issue, and just needs to be "educated" better. Fuck meaningfully changing policies to actually address the issue.

if the issue was a career justice worker [...]

You mean a prosecutor who worked extra hard to lock up over-policed black folks in support of the US prison industrial complex? Justice worker my ass. There is no justice to be had in the US.

America was overconfident [...]

No, the Dems were overconfident that Trump would be so reprehensible they could sit on their hands, change nothing, put up a lame duck candidate at the last minute after dragging their heels for months over Biden's mental state (which was obvious to literally everyone who heard him talk) and somehow still win the election with a bunch of stale policy positions that were and are deeply unpopular.