I’m frustrated with the reflexive “both sides are equally bad”

No one is saying both sides are equally bad. And we keep saying this over and over, and it gets ignored. Just so were on the same page NO ONE is saying both sides equally bad.

...response that shuts down any meaningful analysis of what’s actually happening in our politics.

Ironically it's usually the opposite. Someone will make the lightest possible criticism of Liberals and the knee-jerk reaction to that is "So you think both sides are equally bad?!" That's what usually shuts the conversation down.

sometimes cave to corporate pressure

Try replacing sometimes with "usually". They may be different corps, but almost all of them are in the pocket of one corp or another.

they’ve made compromises that disappointed their base

That's putting it mildly.

I see meaningful differences that have real consequences for people’s lives.

Of course, and again literally no one is saying they are equally bad. You can vote for the less bad option while still hoping for meaningful change.

On issues I care about (healthcare access, climate action, voting rights, ext.) one party consistently proposes solutions and votes for them when they have the numbers.

It's usually weak, ineffective half-measures more designed to look progressive than actually being progressive, but sure if you compare them to literal Nazi's they are saints.

When Democrats fail to deliver, it’s often because they lack sufficient majorities or face procedural roadblocks. When they do have power, they’ve passed significant legislation on infrastructure, climate investment, and healthcare expansion.

So, just as an example when Obama was president and Dems had the majority in both houses of congress, and Republicans were shitting all over themselves proving that they would not compromise a single inch- instead of passing any type of "Medicare for all" or "Right to Healthcare" they passed the highly compromised "Affordable Care Act". Why? Contrast that fact with this statement from Obama prior to the election.

"I happen to be a proponent of a single-payer universal health care program," Obama said. "I see no reason why the United States of America, the wealthiest country in the history of the world, spending 14 percent of its gross national product on health care, cannot provide basic health insurance to everybody. And that's what Jim is talking about when he says everybody in, nobody out. A single-payer health care plan, a universal health care plan. That's what I’d like to see. But as all of you know, we may not get there immediately. Because first we've got to take back the White House, we've got to take back the Senate, and we've got to take back the House."

Odd that when the Dems had "taken back" the White House and both houses of Congress the best they could do was a watered down and problematic solution that still left a lot of people without health care. It's not like compromising on that gained them a single Republican vote.

"Coincidentally" the Healthcare Industry 'donated' over $20 million to the Obama campaign, way more than even the almost $8 million they 'donated' to John McCain. Very odd indeed.

But that cynicism serves the interests of those who benefit from the status quo.

I honestly can't think of a single institution anywhere in the world more devoted to maintaining the status quo than the DNC. Not one. They aren't 'progressive' in any way. Obama didn't even come out in support of Gay Marriage until he had been president for over 3 years, and after right wing Democrat Joe Biden already had. This wasn't due to some sense of fairness or equality, it was political pressure.

If you can’t tell the difference between someone trying to reform a broken system and someone actively working to keep it broken, you’re not offering insight. You’re providing cover for obstruction

By refusing to even hear about potential failings of 'liberal democrats' without engaging in 'whataboutism', it only strengthens the DNC's position as the 'good guys, fighting for reform' when the reality is they are the 'less bad guys, fighting to maintain the status quo'.

Fascists are bad. We all know they are bad. We all know they are worse than a bunch of corporate stooges who want everyone to be slaves to Capitalism, but at least you can feel good they are doing the bare minimum to address the multitudes of problems in the country.

There is a third option, and there is absolutely noting wrong with pointing out the flaws on both sides of the Two Party system and hoping for a future of 'actually good' instead of 'less bad'. Even if it is just a dream, I'd rather waste my life trying to make those dreams real than throwing my arms up and saying "This is the best we can ever hope for".