It's all of the above, really. The Left (actual left, rather than the center right to right wing Democrats in charge of the party) is blaming the DNC, Harris, racism, sexism, the billionaire-owned media, the antiquated political system, and of course the people who voted for fascism. Because all of those things contributed meaningfully to the baffling and tragic result.
Meanwhile, the DNC and their most diehard supporters blame racism, sexism, and most of all the Left.
They obstinately refuse to acknowledge that their "team" fucked up, so they're blaming the people whose warnings they refused to listen to.