To be clear, this doesn't mean that artillery doesn't get used at all. It just means that some assaults go on without artillery support, and most assaults go with a lot less of it than is supposed to be used to soften up a fortified enemy position according to military theory.

Artillery became dominant quite early on, since the initial Russian attempt at blitzkrieg failed last spring, and things changed into something more closely resembling trench warfare. Since then, its extensive use has caused supplies to dwindle. Wagner troops under Bakhmut specifically were high-priority as far as Russian logistics is concerned due to the political importance of the battle, which is why it didn't take them until this past winter to run out - this is when Prigozhin started posting photos with piles of corpses of his own troops and complaining about insufficient supplies. At the time, people from various other units noted that they have been having those problems for much longer, and the unofficial term "meat assault" (мясной штурм) was already in widespread use among Russian troops to describe the way they were fighting by the end of 2022.

Russia uses plenty of artillery in Bakhmut, far more than Ukraine does. But their army has only been successful at taking ground with truly enormous amounts of artillery, like what they were using from April to July of last year. That level of artillery consumption cannot be sustained and without it they have barely been able to defend the land they have much less take new land.