[Nevermark]

> The equations don’t agree with observations so we invent a thing we have not observed to explain it.

Yes, and then implications of the invention are followed up on and dark matter has passed a lot of tests and has strong explanatory power (i.e. parsimony, Occam's Razor) over a variety of phenomena, from small dark galaxies up to the matter web structure of the observable universe.

So it has very very strong evidence behind it, at this point. With an unbroken trend of accumulated evidence.

The reason for remaining questions stem from the fact that the small scale nature of dark matter is not yet characterized. Which differs from all other gravitationally active materials we know of - i.e. all the particles in the standard model.

But we don't know the fine structure of space either, and we don't count that against General Relativity. In both cases the large scale properties of each phenomena, that we can measure and model, provides clear reasons why investigating the small scale properties has been challenging.

In both cases, it is the extreme weakness of gravity at small scales, and the low, if any, alternative interactions with the standard model particles we know well.

[prerok]

The problem I have with dark matter is the name. If I understand it correctly, its existence cannot be predicted. We observe strange results, so we explain it by inventing some strange new concept of mass that's otherwise non interactive.

For example, the dark matter might be mass gathering of otherwise non reactionary particles like neutrons, it could be wrinkles in spacetime that have a similar effect as massive normal matter bodies have, or they could be advanced civilizations that learned how to hide their star systems from the rest of the universe.

We simply don't know. I suppose we had to name it somehow, but the name just sounds wrong. It might not be matter at all. It is also not dark, it's non-reactive.

Why did they not rather choose something like spacetime wrinkles?

[Nevermark]

We know we can't see it (dark, as in not emitting or otherwise interacting with light), and it creates and responds to gravity in the exact same way the matter particles we know do (matter).

The two word choices can be quibbled with, but they form an accurate shorthand for what we know.

If the fine structure is discovered to be wrinkles in space I expect there will be a renaming during a time of great celebration by the future Nobel Prize winners! Especially if that also shone light on space-time's ultimate structure!

Edit: I will humbly propose a name for your postulated tiny space wrinkles: Wrinky-dinks!