The "crimes" narrative is dangerous. It shifts the responsibility as low down the hierarchy as possible, picturing atrocities as incidental rather than systemic. It is lowkey legitimising the invasion: the idea is fine, the execution is questionable

These crimes were not a collection of separate incidents, but merely the aspects of one big crime - the Russian invasion. They wouldn't happen, if Russia did not invade. Therefore, considering them outside of this context = shifting responsibility down the hierarchy
The "crimes" narrative is tangible to the situation in Russia itself. In Rostov regions where the troops concentrate, the violent crimes rate is skyrocketing. This rampage of violence can indeed be described as a collection of separate "crimes". The situation in Ukraine can't
Consider that this is primarily an artillery-centric war with majority of killing being probably done by the artillery. I strongly suspect that in many (most?) cases it would be impossible to prove that this specific artillerist knew where exactly he was firing
I suspect that cases like "a soldier entered a house and massacred the entire family" would count only for minority of killing. In most cases it would be "artillery razed the city to the ground". But this specific artillerist did not know anything, he was just loading the gun
I presume that most of killing in Ukraine is being done indirectly, with extra steps. Simply because artillery, etc. is killing way more people than guns. Proving individual guilt of everyone involved may be very, very hard. Many could claim they didn't even know where they fired