I think this is what the OP is saying though: There are many ideas about what dark matter is or could be, but astrophysicists model the early universe using only baryonic matter, the results _are wrong_.
As a theory, it's quite simple: in its absence, the physics doesn't work. If you add matter that behaves in a particular way, simulations align to observation.
What is dark matter? shrug I don't think we can call any answer to that question a theory yet, we don't have any way to falsify it. We have many hypotheses, but those aren't theories.
That doesn’t make any particular theory correct. It is only proof that our current model is wrong.
Filling the gaps with math, and calling the math “dark matter” does not make dark matter correct; one or more of our existing models is wrong.
They actually don't, numerous extra parameters have to be added for DM to account for observations. DM was invented to fix one problem with observation, and 15 more have cropped up which don't fit.
[1] From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity, https://www.mdpi.com/2073-8994/14/7/1331/htm
I mean do we really believe that we know everything about this? Somehow, we A) know we have large knowledge gaps, AND B) believe that we understand things we have unanswered questions about.
We have a LOT of confidence about dark matter and exactly zero direct evidence.
It seems much more likely to me (I am not a scientist) that we are wrong about things that we assume to be hard facts and those error(s) have artificially produced the need for dark matter in order for things to make sense.