The question you should ask is why Bakhmut is so important to the Russian.
For the Ukrainian, their goal is to hinder Russian offensive, either to slow their advance or to buy time for their own counter attack. Which mean for the Ukrainian, any fight is welcome because it take resource and focus off what they are doing. As long as Russia keep attacking Bakhmut, Ukraine will say "Why not"
For the Russian, Bakhmut is not important AT ALL since they loses Lyman and Izyum, because before you need Bakhmut to secure a flank to attack Sloviansk and Kramatorsk which is the only way you can take both city, but now with Izyum and Lyman under Ukrainian Control, that is no longer possible, on the other hand, Bakhmut would be sitting duck even if Russia took it if and when Ukrianian broke thru Svatove.
What Russia is doing now is basically wasting resource and stringing up their troop for some land you don't need to have or have no purpose at all, they already did it twice, focusing on Mariupol means they blunted their Northern Advance and give time the Ukrainian build up their defence to withstand the Russian Assault, which is why it lead to the current situation to begin with. The other time they so focus on Siverodonetsk and Lysychansk they lost both Kharkiv and Kherson because of that.
This is not a smart way to fight.