Exactly, it's a fine balancing act where Russia doesn't want NATO to provoke a major escalation with NATO, and they're just dragging out a war of attrition because it's working in their favor. A big offensive would also be a lot more costly, so I really think that the plan is to just slowly keep ramping up pressure until Ukrainian army starts to collapse.

Mearsheimer had a pretty good analysis of the situation in my opinion. He points out that vast majority of casualties in the war come from artillery and Russia enjoys a massive artillery advantage over Ukraine. So, attrition ratio favors Russia in a big way.

Experienced and motivated soldiers are the core that holds Ukrainian army together. And as these soldiers are lost and replaced with new conscripts who lack experience and motivation the army effectiveness keeps decreasing. Eventually it will hit an inflection point where it's simply not capable of holding the line.