That starts out well but then the language changes in the way I described:
> Dark matter is not known to interact with ordinary baryonic matter and radiation except through gravity,[b] making it difficult to detect in the laboratory.
The properties/interactions of DM are defined by our observations rather than observing that it doesn't interact with baryonic matter. You can see how replacing each mention of dark matter with 'the unknown cause of anomalous gravitational observations' is the same minus the belief that it's a particle. This is why I question its theory'ness.
Theories proceed from observations. Based off the observed anomalies and our knowledge of the Standard Model, we can say a lot about the properties of Dark Matter - if it exists.
Going forward, we have two choices:
1. Develop another explanation for the observed anomalies (the so-called MOND theories). So far, these have all failed. Turns out GR is incredibly difficult to both replicate and extend.
Can the theory of dark matter fail? If we never find evidence of such particles, that only means we haven't found them. But we can never rule out their existence.
It becomes a game of statistics. Once we believe we have the capability for detecting dark matter, then each experiment failing to reveal dark matter works against their existence. Keep in mind we can't rule out the existence of Unicorns, either, but that doesn't mean we seriously believe they exist.
> Dark matter is not known to interact with ordinary baryonic matter and radiation except through gravity,[b] making it difficult to detect in the laboratory.
The properties/interactions of DM are defined by our observations rather than observing that it doesn't interact with baryonic matter. You can see how replacing each mention of dark matter with 'the unknown cause of anomalous gravitational observations' is the same minus the belief that it's a particle. This is why I question its theory'ness.