ujm,
“Russia is not party to the Rome Statute of the ICC and its rules are not international law binding upon non-signatories.”
Russian individuals can still be accused of war crimes and arrest warrants issued, even if Russia refuses extradition or recognition of the court. A special tribunal can also be initiated specific to the conflict in Ukraine. But at the end of the day your point is irrelevant – not recognizing an international court does not redefine what a war crime is.