The false equivalence of doing the "both bad!" song and dance serves to so radically under-emphasize the absolute wanton, orders-of-magnitude-worse levels of corruption and evisceration of norms of one side by reducing it to "more bad than the other but they're both very bad." It allows the window to shift to normalize the sort of destruction of systems we're seeing by hand waving away how "the other guys aren't great, either!" It's borderline discourse malpractice at this point, and should be called out as such.
While the right is comfortable holding their nose when white supremacists hang around because it gets them a bigger coalition, the left will excommunicate someone for saying out loud that they think trans women are not exactly equivalent to biological women. This shrinking of the coalition is how we ended up enduring another Trump presidency.
Not to mention the complete fiasco that was the 2024 presidential race. We should have thrown out the entirety of DNC leadership several levels deep for letting that happen.
From an outside perspective the US does not have a political left. The policies proposed by the Democrats are roughly in line with the mainstream right-wing parties in the rest of the world. A mainstream left-wing party would look an awful lot like someone like Bernie Sanders - and we all know the Democrats would rather platform a wet paper towel and lose than see him gain any kind of power!