Dark Matter is a very elegant and simple theory, I have no idea why anyone would describe it as crappy or contrived.

I can understand why OP frames his question that way. Dark matter is a kind of spooky-seeming explanation for what appear to be fairly mundane phenomena.

Imagine a 100-kg person getting on a scale in his bathroom and getting a reading of 2000 kgs. Saying that the person is accompanied on the scale by 1900 kgs of matter which can only be detected by the scale does seem contrived. At least compared to the much simpler explanation that the measurement process is flawed (someone's scale isn't working correctly).

In the case of dark matter, it's hard for a layperson to let go of the easy-to-hand, reasonably simple-and-elegant theory that our measurement methods are just mistaken. In comparison, inventing a totally novel type of matter which can only be detected by these same measurement methods...does require some leaps of faith.