Yeah, this is _the_ reason I started using Kagi. The default results aren’t significantly better than Google/Bing/DDG, but being able to block and boost domains is a killer feature.
I was just about out of my free searches on Kagi before I ever realized it could do this. That feature converted me to a paying user (although I've got browser plugins to block domains from Google search, but boosting is something I can't do there).