As my understanding goes the models used are there to see what would be needed to replicate the current best know state of the universe, given what we know about its beginnings and as said its "current" state. Running very many different scenarios the best models need something the astro "community" came to call "dark matter".
As long as a opposing theory can't replicate these simulations from initial state to known "now" state without the use of some form of "whatever" it is quite interesting to call out that there is nothing like "dark matter" (whatever this something may be).
As long as a opposing theory can't replicate these simulations from initial state to known "now" state without the use of some form of "whatever" it is quite interesting to call out that there is nothing like "dark matter" (whatever this something may be).
But that is just my layman's take.