(Disclaimer: am particle physicist, but not a cosmologist) For a bit of context, see Sec. III.6 of https://arxiv.org/abs/2105.05208 ("Challenges for ΛCDM: An update", where ΛCDM is the "standard model of cosmology"). The linked article refers to _known_ problems that this model has describing small scale structures. That dark matter doesn't exists seems like a non-sequitur to me.