I don't even understand why Google doesn't allow blocking some sites in search results. Paid ads, I understand, these generate profits. Although Facebook still allow me to remove some ads that I don't want to see. But unpaid SEO rubbish, how does it benefit Google at all? If anything these parasites bogs down the quality of search results
They had a feature to block domains from search results in the past (like, 10 years ago). It was removed. I don't know why, but it feels like exactly the kind of feature that sounds great on paper but doesn't actually survive contact with real users.
First, I'd bet that very few people are actually interested in doing that kind of manual curation or engaging with power user features. How large a % of users need to interact with this for the feature to be worth maintaining (in all the backends and frontends)? How many of them actually do so?
Second, the task of blocking spam is adversarial and sisyphean. Trying to deal with web spam by domain blocking (with an individual blocklist) would be like trying to deal with email spam with your own blocklist of spam words. The results will be worse than whatever can be done centrally, where much more information is available both on the sites and on how users actually interact with those domains. And even if you managed to make a good blocklist for a point in time, your job is not done. Tens of thousands of new domains will have popped out next week.
(The dream here of course would be to use the block decisions from individual users to drive the centralized protections. But unless legit users are actually using this in very significant numbers, it'll quickly become just another abuse surface. E.g. brigading, "downrank your competitor in the results" as a service, etc.)
Third, some people will probably block domains they shouldn't have blocked, and then have a bad user experience in future searches as the sites with genuinely best results is blocked. And then you're only left with only bad options: ignoring the users' stated preferences which they'll hate, or serving bad results that they'll also hate.
Can the feature work for a different search engine? Sure. For example, what if you have a paid search engine only used by power users and are looking for a simple to explain feature that people think they want to entice them to sign up? It'll be great for that. And if your entire user base actually loves and uses the feature? Well, it becomes a feature worth maintaining and expanding; it'll actually be a high quality ranking signal rather than something that's trivially gameable; etc.
I'm not trying to block domains from my search results because I'm afraid of spam. Google does a pretty good job of not putting spam in my search results.
I'm trying to block particular domains because I know the websites hosted on them are utter garbage, and better alternatives containing the same information exist.
It is hard to filter out SEO rubbish with a low rate of false positives. Spammers became really good at pretending to be real sites.
For mail spam various trust-based solutions like server black lists, domain verification etc. were important to solve the problem. But Google has little incentives to push for a trust-based search due to their business model.
