Hard to say.

Problem is that this is exposing Ukrainian forces to attrition, too.

Hard to say. Certain is, the Russians want not only Lysychansk but entire Donbass at (almost) any price. Thus, imposing attrition upon them is always 'good'.

Problem is that this is exposing Ukrainian forces to attrition, too.

In this regards, it doesn't matter if this is happening in Severodonetsk, Lysychansk, Siversk, Sloviansk or Bakhmut: where there is difference is IF this is buying time to train additional Ukrainian troops and get more of NATO weapons (and supplies).