The jurisdiction part is the key here, IMHO.
Sure, the likelyhood of reliably tracing a single attack to a crew is very low, but a prolific crew has dozens or even hundreds of attacks going on in parallel, so tracing just one of them should be enough to take them down.
However, most crews live in "bullet proof" jurisdictions, where we cannot reach them.
If this practice of ransomware attacks continue, we really need a better solution for that. This could go as far as cutting off the "bullet proof" countries from the Internet, if it weren't for China and Russia, that simply from an economic and political perspective, we cannot disconnect.
I guess diplomatic solutions are needed, as well as investing more in IT security, secure OSS etc.