They provide same functionality as DNS[sec]. You are not at whim of a corpo, nobody can suspend you, corrupting or hijacking records is pretty much impossible...
There are already many anti-phishing solutions: Chrome has a built-in phishing database, it shows a warning in place of a phish web site. Many VPN and anti-virus software packages come with bad site blockers, it can be done on DNS resolver level, etc.
This is a free market solution: different vendors can compete in phish detection, and users can choose one which works the best.
There's really no need for TLD provider to do this.
And we see why it's a bad idea: a mistake can lead to thousands of legitimate sites being kicked off.
Why are you advocating a solution which is clearly inferior?
If we treat Blockchain as a database with specific properties, and use that to back DNS, then we have a DNS system with those specific properties, instead of the system we currently have, which has different specific properties. Some of those properties are desirable, but as we see here, some of them are not.