Blame is an overrated concept. It only serves an instrumental purpose. It can help us make better predictions of how people will behave in the future, but it has no inherent value. Mechanically, liberal shittyness and their contributions to rising fascism means we can predict how much support they'll give us. It shows what matters to them and the calculus behind their actions.
Often they make their imprudent decisions because they have an inadequate understanding of the human ecosystem. They don't consider how the economic suffering caused by deregulation and policies that favor the rich are the system's biggest existential threat. Politicians worry about their political existence instead of the system's existence. When fascism is at the gates, preservation of the system matters more to their personal existence.
This is probably why you think leftists have a bargaining advantage, and they do. The left can allow liberalism to suffer, but they'll suffer with it. It's a game of chicken, a gamble, and not the only tool the left has. They could, and this might shock you, focus more on local politics and primary elections. They don't need to play chicken to get a leg up on liberals; they can win primaries and build leftist sentiment while doing so.
The DSA has 3 current members in congress, who represent ~2.25 million Americans. You might scoff at this small number in the grand scheme of things, but you also might not know how tiny their actual membership is. They have never had more than 100k active members. They've elected officials while being a similar size to lemmy, this tiny corner of the internet. And those are just current DSA congress members; there are 3 other former members in office because of DSA support.
Leftists often believe electoral politics are a waste of time, yet they're ignorant of how much it has affected their current movement. Obama's ACA might have sucked, but it made single payer a significant part of the conversation. With no ACA, Bernie wouldn't have basically won the 2016 primary, a presidential run that made socialism a far more popular idea in America. Current DSA Representatives have promoted leftist ideas and positions more than they've affected votes in congress. They're a handful of votes, yet they've provided a dissenting voice to liberal slop.
Most of the people who vote for DSA members are left leaning liberals; liberals who have played a greater role in promoting leftism than any proud anti-voter I've ever met in person. I'm not saying you need to join the DSA and volunteer for their candidates. Just spend a few hours of your year voting.
Even if you still don't vote, VOLUNTEER IN YOUR COMMUNITY FFS. Local politics, electoral or otherwise, are the backbone of every single successful movement. Provide services to those in need. Follow cops around with guns. Educate people about politics. Do the leg work to improve lives. That's what earns trust and support. Providing