You should consider that only a very small amount of phishing domains and URLs ever make it to phishtank,openphish and similar services.

I welcome what the author is doing but you need to do a bit more for phishing protection, like blocking newly registered and/or uncategorized domains.

I wonder if there are browser extensions for this sort of stuff?

Yes there are browser extensions that offer phishing/malware protection

https://malwaretips.com/threads/updated-3-6-18-browser-exten...

You could block all domains that are not part of the Majestic Millions[1] (the million most common domains)

[1] https://majestic.com/reports/majestic-million

This is not very scientific.

Agreed, and very light on the technical. A few months ago when I was working on setting up a pi-hole with and testing DNS blocking, I came across a few articles like this. Long story short, I could not find a -verifiable-, in depth and even slightly scientific method approved study for the major free services. Ended up going with blocklist on the pi-hole and using quad-9 just for the DNSSEC addition. No problems so far, and not buying into the other snake oil.

What about false positives?

I doubt that the free OpenDNS is maintained now.

It is, but the OpenDNS resolver tested is for FamilyShield which is only advertised as blocking "Tasteless, Proxy/Anonymizer, Sexuality and Pornography."