As a non-leftist and therefore an outside observer on these things, it seems to me that the "left" (= Democrats) really blew their messaging from, say, 2016 to 2024.
They moved too far to culturally left issues (gays, trans, and immigration, in particular), to the point that they lost the factory workers who were economically liberal but socially conservative. Those people were made to feel that if they had reservations about gay marriage, or trans people in womens' sports, or immigrants in the numbers (and lack of documentation) that were happening, then they were viewed as moral lepers, incapable of redemption by anything short of permanent abasement for their views. There was nowhere for them to go that would represent their economic interests without cultural suicide.
Well, that didn't work out for the Democrats. Too many of their normal base of voters (the blue collar workers) turned their backs, and we got Trump twice.