They’re human like everyone else, and try to use language that is specific and descriptive. In this case the word direct observation has become to mean something very specific In the field of astrophysics. It’s not out of malice or anything, just results from the difficulty of scientific writing, so you use words that already have established meaning.

Direct observation ≠ direct detection

I would argue that dark matter is much more based on indirect observation, things like rotation curves and baryonic acoustic oscillations.

Confusingly, direct observation does not mean the same thing as direct detection.

This study “directly observes” a hypothetical dark matter signal. However this is distinct from direct detection experiments, where a dark matter particle is found in a collider.

I am a physicist, studying dark matter.

Firstly, It would be nearly impossible to prove that dark matter definitely does not exist.

And secondly, there are no alternatives to dark matter that come even close to explain our universe as successfully as dark matter.

That doesn’t mean it’s right, but any explanation without dark matter is not favored IMO.