Shameless plug, but I've been working on a project [0] that does exactly this. Currently it just has a few filters I've created for myself and only supports web search (and a few !bang like re-directs), but I'm working on implementing user accounts that will be able to create their own filters.
Yup, that's exactly it. I've found that there are certain websites that I have basically no interest in seeing. Eventually I might incorporate more granularity to get sub-domains or something like that, but for now it's just whole websites based on URL.
[0] https://hadal.io