Scientists are not prone to falling back on explaining observations via postulating a new kind of matter we can scarcely observe. Ever since the first indications of "dark matter" scientists have been attempting to explain it as something more familiar to us, some kind of atomic matter or some-such, maybe gas or dust or lots of planets or dark stars or something. At every single turn they've been stymied, and instead of eliminating the idea of dark matter as an ethereal particle they've instead eliminated other possibilities.

Don't look at the current theory of dark matter (weakly interacting massive particles) as some hare-brained scheme that scientists thought up, instead look at it as the hard-fought victor of numerous observational challenges. Dark matter is the theory that survived. We tried explaining things a zillion other ways (gas clouds, compact objects, neutrinos) and those theories just didn't match the observations. There are also a few exceptional circumstances (such as the bullet cluster) that indicate very strongly that dark matter is something different than either gas clouds or stuff like stars and planets, because in the bullet cluster we can observe the gas and the stars and planets and the mass, and each of them are in different places because each of them follow different rules when it comes to interacting during a galactic cluster collision.