Democratic politicians aren't making any serious shift to the left anytime soon. Politicians' policy follows the voters, and "the left" is a fickle group. I mean, any serious leftists would have voted for Kamala, because what the absolute hug, you're just gonna let Trump win again? He just held a damn Nazi-cosplay rally in Madison Square Garden. Any group of people that weren't motivated enough in 2024 to prevent a second Trump presidency is never going to won over by any Democratic candidate.
Additionally, I just don't think there are enough progressive-left voters in America to support a presidential bid. As much as I hate to say it, we are a much smaller group than we want to believe. The hardcore-left needs rid itself of purity culture and start building coalitions.