Well, I'm not COMPLETELY ignorant, but not knowledgeable enough to make emphatic declarations, so I see your point.

With so much matter unaccounted for, how is it certain a more distant gravity source isn't pulling the superclusters (and everything else)? I'm not saying that's the case, I'm just curious how we can KNOW that's not the case.

Yeah, but I'm a lot more comfortable with that. We know no theory perfectly explains all the evidence, so there's a known but undefined amount of inaccuracy in every theory. Reducing that inaccuracy through observation, hypothesis and experimentation is what I hope is occurring, up to and including completely abandoning any theory with as much or more evidence against it as for it. Maybe I am just giving into the sensationalism again, but it seems like dark energy is more than just a wrinkle of the cosmological constant. That's not necessarily a bad thing; if it becomes a complete revision justified by the evidence then I have no complaint with it--provided it IS justified by the evidence, not just a desire to replace an existing theory.

The distinction was that we'd expect a unique fundamental particle to have unique properties, but positing multiple particles with most or all of the same properties would make the properties no longer unique. That's what I meant by comparing them to neutrons and protons: They were recognized as different particles due to different properties; had they possessed all or most of the same properties with slightly different masses they would not have been considered different particles (and, in the sense of both being baryons, no longer are) but variations of a single particle. The notion of multiple fundamental particles with only a few slight but critical variations reminds me of how we were tipped to the existence of quarks in the first place.

I find your surplus of faith disturbing. Professional communities, the scientific among them, can and have made mistakes, sometimes big ones. I'm confident any such error will be caught eventually, but can't help remembering that "eventually" is the word Wikipedia uses to describe how other scientists ultimately vindicated Vera Rubins findings on gravitational rotation, which it also says were met with skepticism until then. Institutional errors happen, and thus no discipline is infallible collectively or individually. EVENTUALLY quarks were hypothesized (and also met a fair amount of skepticism) and eventually they were found, but prior to the former particle physics went through a period where list of new "fundamental" particles never stopped growing. Not centuries ago, but about fifty years ago. Certainty that "science marches on" and never needs to retrace its steps except briefly is, once again, less than reassuring since it's reminiscent of the same certainty that has led down many blind alleys.

If that's what you've observed I'm in no position to dispute it.

OK, I'll wait and see. I still can't help thinking about the proton decay GUTs predict. Perfect Symmetry contained the statement that "we know in our bones" protons have a half-life>10^30 years because our bodies own radioactivity would kill us if they didn't. Neutrino detectors had recently established their half-life had to be>10^31 years because we hadn't seen any decay, so the GUT creators revised their theories to more complicated particles that only required a half-life of 10^32 years. Then bigger detectors ruled that out; more revision, more complexity, more observation. Recently crusing through Wikipedia I saw that the minimum estimate is up around 10^34 years and there's a real prospect we'll NEVER be able to build a detector large enough to reproducably observe proton decay, and still the revision and increased complexity continues. The possibility the theory might just be WRONG doesn't seem to have ever been on the table; there's too much fame to be had from achieving what Einstein attempted and failed.

But, OK, I know I'm out of my depth. I'll see what happens and hope that if any observer bias exists it's corrected sooner rather than later.