How would this practically work?
Because any 'country' could feasibly be responsible for a pandemic. If China has only a handful of cases, but countries completely fail to address it, how do you quantify culpability and contributory blame. China might well say 'we did as much as we could and gave been successful. It's your fault if you have let it run through your population'.
Does the UK take responsibility for spreading variants across the world through flights or lack of adherence to isolation? Do countries of new variants take any responsibility?
It was Chinese negligence that led to the circumstances for a virus to emerge. They had the warning with the wet markets, this isn't the first virus to emerge in this way.
Negligence should mean they are held responsible, to the point where they pay massive reparations to the world.
It won't happen, but it should happen.
Your reasoning is akin to someone releasing a rabid tiger into a shopping centre, and then blaming those attacked for not defending themselves. It doesn't make sense. Ultimate culpability rests with China and China alone.