It's true that encryption is useful despite not being perfect but there's an important bit of missing context: blockchain systems are being sold as suitable protection for people “living in a corrupt authoratarian system” and that changes the risk calculations considerably.

If you live in a relatively open democracy, the knowledge that your encrypted chat app could be attacked by the police isn't a huge deal because there's a legal process protecting you but that trade off changes considerably if you are at risk from a hostile government. Systems which require you to leave a public paper-trail for the authorities, for example, are too risky to consider and something more privacy oriented is still a significant gamble — especially since in such an environment it's likely that you'd be at risk simply having it installed on your devices unless you were certain that it made no identifiable network activity. If I lived in China now, for example, I would not want to risk having something like a VPN client or Signal installed on my phone if the police stopped me or started linking DNS lookups to ISP customers.