But that's what the physicists have tried (and not been successful at so far). The issue is that modifying how we think gravity and matter works is not just a

But that's what the physicists have tried (and not been successful at so far). The issue is that modifying how we think gravity and matter works is not just a change in a math equation. Changing those equations would also mean a whole chunk of modern physics, including general relativity is wrong - yet all those theories can be observed and confirmed in many very different ways to be consistent and valid. So if you change those equations to adjust for dark matter, they no longer give the result for many other phenomena that we observe.