Secure from whom? A school IT admin? An abusive spouse? A kiddie with a wifi packet sniffer? From hackers going after email accounts? There are lots of threat models that CryptoCat was useful against; and in the long run, CryptoCat was right about usability.
How about "secure against the best funded, best staffed signals intelligence agency in the world"? Because that's the adversary Cryptocat ended up with. When it came out that Greenwald had used it for Snowden, Kobeissi was over the moon about it on Twitter; he treated it as an endorsement.
