Fair enough. Perhaps my take was slightly hyperbolic.

Gun control is a great example of something Democrats can't agree on. We have gun-grabbers, background-checkers, and even a few NRA-hawks. Details on Healthcare. Reparations are a 50/50, too. The thing in all of those, I think, is that we're willing to compromise.

Actually, looking at some of your bullet points, I see them as party compromise points. Prior to Dobbs, there was a LARGE percent of Democrats who supported what they called "reasonable restrictions" on Abortion, and many still do if tapered by seeing how slippery the slope really was. And going back 10-15 years made it even more of a mixed bag. Pew couldn't get more than 63% of Democrats to agree abortion should be legal "in most cases". Back when Roe was precedent. The thing was, we could all compromise on which cases, and agree that "in no cases" should never be the law of the land. The more anti-choice Democrats were willing to compromise on some propaganda, parental shame forms for underage, etc.

Ditto with healthcare. It's a sad truth, but most Democrats didn't want to see a Public Option in the ACA. It looks like the trend of "Public Option" being fringe flipped in 2020. Probably not a coincidence. I can't find party-split polls pre-2020 right now, but a 2019 poll showed fewer than 25% of Americans wanted a Public option. Even if it was mostly Democrat-leaning voters that said that, we're still looking at less than half. Now, admittedly, we're approaching 70% of all voters who want some sort of public option.

I honestly can’t think of any other topic that Democrats disagree with each other as strongly about.

FPTP Voting, details of abortion rights/restrictions, details of how to handle healthcare. Lots of Freedom of Religion and Freedom of Speech disagreements that just don't rise to the level of "headliner issue". I'd say any copyright/dmca question is "it's complicated" to Democrats who are informed enough to even speak of it. I can't find numbers on the wealth tax, but they seemed mixed back when Warren was pushing it. Topical to the above discussions, military isolationism vs "world police" attitudes. These are all fairly contentious issues within the United States. Biden seems to represent the plurality view on most of them, which I give him credit for despite my having very different opinions.

EDIT: To clarify, it's a bigger gap for a bigger reason. Almost exactly half of Democrats are neoliberals. And our progressive caucus, almost as big as the neoliberal wing, is diversified between capitalist-progressives, socialists, and other incompatible but good-faith groups. On the big issues, we're either all in compromise or in agreement on a few large bullet points. But on the less-highlit issues, there are fundamental foundational differences of theory of government within our party. The biggest families of issues on that are:

1. The nature of money and which economic attitude to hold on things like supply and demand
2. The type and amount of regulations, or workers rights, that should be enforced vs limitations on businesses (or neither/both).
3. How much power a president should be able to hold, and in what domains

The list goes on. For object example, I'm a passively-anti-union progressive. I think Unions are band-aids. I think they should have all the rights and protections they have, but they are a sign of capitalism remaining dominant with regards to worker laws, and our goal should be to make them useless by making them unnecessary. There's a lot of Democrats that would vote anti-union, but despite my position, I'd vote pro-union as a compromise for my real wants. However, given the option between writing a union protection or a worker protection into a bill, I would fight tooth-and-nail for the worker protection. Many Democrats would fight for the union protection instead.

I mean, what does Means-testing look like WRT welfare in the Democratic party? We're all over the place. People like me say it should be available to everyone regardless of means, where some Labor-friendly neoliberals are happy to leave in "employed" clauses, but want to loosen the income restrictions so that hard-working Americans get the greater benefit. Obviously I am sympathetic to that position as much as I disagree with it.