Part of why dark matter is such an attractive explanation is because there are no constraints on it. Unfortunately this seems to have relieved pressure to explore and test modified gravity.

But you are correct, I don't know what I am talking about which is why my comments were phrased in the form of a question or literally with the words "I don't understand"

Something like this?

https://chandra.harvard.edu/xray_astro/dark_energy/chart.jpg

With Neutrinos we know how they are created and have a very good upper limit on how much there should be and it's not nearly enough to explain the observed effects. Same for the CMBR.

I'm not saying there couldn't be much more Dark matter/energy than neutrinos or photons but it's a bit too convenient to introduce a variable that is allowed to take any value and match it to observations without an explanation of what it is (besides having mass) or how it is created.

We won’t find dark matter in your or my lifetime, because it doesn’t exist. It is a convenient, flexible, and inelegant fudge factor.