It means that reading about dark matter (and energy) always reminds of reading Perfect Symmetry in HS twenty years ago and thinking, Do these guys just posit a new particle for every otherwise inexplicable observational anomaly? Just because it worked the first couple times doesn't mean it should be the automatic response, and certainly not the only one. The same book naturally discussed searching for proton decay with neutrino detectors, which increasingly looks like a fools errand; even if the lowest half lifes still technically possible are valid it's unlikely we'll ever observe proton decay, let alone reproduce that observation under identical conditions. Looking at the history of what's been invalidated is why, although we should certainly test every theory when we can, I'm a lot more interested in the LHCs unexpected revelations.

Most of the Holy Grails in particle physics do at least allow proof of their existence, however; most definitions I've seen for dark matter and dark energy (which mainly seems an explanation for dark matter not covering all the bases either) seem to make them unverifiable by definition (if not as badly as my favorite such example: Branes).

A modification of an existing theory. Maybe I'm being a little semantic here, but it doesn't seem like a revision on the order of what Relativity did to Classical Mechanics. Most of my objection really boils down to giving it that kind of gravitas; there's no reason all or even most normal matter must reflect or emit energy visible from Earth, and good reason to think most of it doesn't. If by dark matter and dark energy we simply mean normal matter and energy we can't observe or haven't, sure, I'm on board with that, but if we're talking about some exotic and unprecedented form of matter or energy I'm not convinced of the need or evidence.

It probably wouldn't be, and given a choice I'd prefer dark matter, but positing it as matter we can't see because it's too far away from us and/or any energy source makes a lot more sense to me than positing it as matter that literally cannot be seen, by us or anyone.