Given that Russia has massive artillery superiority over Ukraine as well as dominating the air, it's pretty clear whom the attrition benefits in this war. Russia didn't just rush Avdiivka out of the blue. They were putting pressure all across the front for many months now because they have more troops and more equipment as even western media now admits. This forced Ukraine to run their increasingly depleted reserves around to plug holes, and eventually there was going to be a collapse in the front. This is what we're seeing in Avdiivka right now. This wasn't an ordered retreat. This was a disorganized rout of Ukrainian forces in the area leaving wounded and equipment behind. Even western media is admitting this:

Ukraine failed to safely evacuate all of its troops from the eastern city of Avdiivka during its disorderly retreat over the weekend, despite claims from its new top military commander that the move was designed to save lives and avoid encirclement by the advancing Russians.