Earlier simulations comparing cold dark matter models (with dark matter particles that are thermal relics with masses on the order of 1-1,000 GeV), with warm dark matter models (with particles typically around 2 keV), reveal that warm dark matter models produce results much more like what we see in the real work than cold dark matter models.
But, those simulations contained important simplifications, most critically, not meaningfully including the effects of ordinary baryonic matter on the overall evolution the the large scale structure of the universe and particular galaxies.
A new paper argues that many of the problems that the older models found with CDM models relative to WDM models are fixed in more sophisticated new simulations that appropriately consider the impact of a mix of ordinary baryonic matter and dark matter, rather than simply modeling pure dark matter systems.
Meanwhile, an epic 170 paper comprehensively explores alternatives to the standard lambda CDM model of cosmology that modify gravity in the weak gravitational field regime (an idea that started with Milgrom's MOND theory but has many modern variants) rather than relying at all or at least as heavily, on a dark matter hypothesis. Despite its length, it is only a preliminary survey and does not provide a definitive resolution of these questions.