That crypto has to become real money at some point. If the ransom is in something like bitcoin (very common) then identification is just a waiting game for that conversion

Funny that you should mention that. It looks like there is an emerging interest to go after the money outlets: https://krebsonsecurity.com/2021/04/task-force-seeks-to-disr...

I doubt that any of the ransomware people will use any crypto exchange.

I suspect there is whole network of people that will sell crypto for cash to people who want to buy drugs/other things on the darknet.

Maybe there is a handful of corrupt exchanges but the bigger ones already check where your crypto is coming from.