Russia Ukraine war, page-212521

You're forgetting a very cucial part of the story, that being why did Nato have to intervene against Serbia?

Correct, that would be because Serbia was committing crimes against humanity throughout the Balkans for almost a decade.

Serbia didn't stop their crimes against humanity despite being asked, told then warned.

Nato stopped Serbian crimes against humanity.

Exactly the international system of law and order the civilised world needed at that time.