I'm pretty sure you could drop at least 60% of domains from search engine indexes with no reduction in result quality. (And it would probably be a net quality increase to get rid of all the domains that just copy content from other domains, content-farms, scam sites, etc.)
Apropos of anything else, it's one of the things I like about Kagi for search. You can tune a domain to be heavily bumped, bumped, deranked or heavily deranked.
