There are many way to do money laundering. Even if those hackers use worthless new coin but they agree with the value of it then it is works. Law enforcement should focus on the hackers. I think even if bitcoin is not exist those hackers will still have desire to hack to get money. The problem is the human not bitcoin. I am pretty surprised that some people has that way of thinking.
One of the new ways that scammers are currently using to launder money is with NFT. You must know by now the price of NFT is insane. A single NFT image is even worth hundreds of thousands of dollars.
Apart from that as you said about creating a new coin which is planned and then RugPull happens, that is also a scammer scam.
Not just Using Ransomware, Ransomware is just a tool that can be applied to any crime. Even if there is no bitcoin, fraud with other methods will still exist and the target is of course users.