Who takes responsibility for a thief who stole someone's digital goods and escapes without punishment in decentralized cyberspace?
Decentralized cyberspace for not everyone. It's not for granny and grad pas who do not know how to use keyboard, how to browse internet and exchange messages securely. If you have not heard about encryption, done a little study about cryptography, if you do not know how to keep digital asset safely then crypto is not for you. For your own fault do not blame and entire idea.
To answer your question in one word,
YouYou are responsible to secure your asset.
Actually no one can steal cryptos without the owners who made mistakes whike storing their private keys. So the actual owner is responsible if he ever lose his crypto assets.
I still know people who save their private key in Google keep and in other digital platform which they think is secure. They argue google do not have anything else to do to check what I have stored in my Google keep or they think there will never be a data lose in google or in those digital platforms. If anyone is that much stupid then let them lose their money. Let them learn from the mistakes when they will not simply learn from other's experience.
Son, if tomorrow somebody kidnaps or rapes your child, you, like a keyholder of your child's freedom, will be responsible because you haven't cared enough, right?
Are you saying kidnapping and rapes are not happening now and they are not asking to give you money.