That's great, until they decide to nix it or you want to migrate your list to another search engine. I wish we could decouple these choices from the website providers. A web browser that puts the user back in control.
There is no reason to think that a paid search engine like Kagi will get rid of one of it's signature functionality, but if you're interested in an extension for browser: https://github.com/iorate/ublacklist