How so? I was always taught/told (in the context of science and science class) that it’s better to not have an explanation than to not know how to explain something is and just go with something out of pressure.
Who is doing that? Your comments all seem to imply that you think dark matter is something scientists just randomly assume to be true, and I don't know how to explain that you're misunderstanding this beyond what I already wrote.
This is that in practice as I’d rather wait, for example, to have better instruments to see if Planet 9 (which there’s a demand to identify with clarity since we suspect it to keep hurling small bodies into the inner solar system) is really dark matter (however we might identify it) or if it’s an obscure planet, a small black hole, or a phenomenon we don’t even know about yet.
But what do you want to wait for? Unless people think about what could be causing the gravitational anomalies we're seeing, we won't come up with better instruments. But you don't want people to think about that, because they can't fully explain it. So how do you get to better instruments?
Science works by observing phenomena, formulating a hypothesis to explain them, making predictions with that hypothesis, and finally testing (and refining) it. Scientists have observed gravitational anomalies, they've formulated many hypotheses (of which dark matter fits the best so far), and now they're trying to make predictions and test them. This is really difficult, because we're far away from the gravitational anomalies that we're seeing, and they aren't interacting with the electromagnetic spectrum. What exactly is your issue with this process? You keep saying that scientists assume things, but I see no violation of the normal process, and no better theories.