Scientists used to think that life did not exist beneath the photic zone. Then they dredged deep sea sediments, and they found organisms. In your example, the problem is that the observations are not complete.
Exactly. The point is that our observations are formed by the tools by which we measure the world around us.
That's a "negative" claim - one which can be disproven with a single counterexample. Such claims are extremely difficult to establish, because you must test and rule out all possible counterexamples.
Yeah. But how will you find a counterexample if your net doesn't catch anything smaller than 5 cm? Or if you don't even realize that it is the net size that determines the size of your captured specimens?
The existence of DM is a positive claim. If is far easier to establish, and in fact it already has been by multiple lines of independent evidence - including the direct observation of its gravitational lensing effects.
Look - there is a (reasonably) unambiguous mathematical formalism for handling this question of what is extraordinary and what is not. You can take either a Bayesian or frequentist approach, but they both give the same result - DM is by far the least extraordinary theory we have. Until or unless someone comes up with an alternative, it will remain so.
I'm not arguing against DM.
I reject that.
How long have we been using telescopes? A few hundred years. How long has a well codified scientific method been actively used. A few hundred years.
And you think that it is surprising that we are discovering new "stuff". That is an extraordinary view.
Absolutely.
We are not uncovering the last remnants of knowledge about the universe. We have merely begun to scrape the surface of what can be found.