When searching for specific topics, I tend to get a lot of blogs/pseudo-news sites listed. Many of them tend to be anti-science or revisionist. When I block one of those sites, I want that similar sites (so: appearing often together, endorsing each other, or otherwise related in a graph) also could be downranked. I expect search quality (and user experience) to increase, but a limitation could be downranking useful information about those sites, and of course abuse of such mechanisms.
Blocking would be more useful in many usecases such as limiting disinformation, low quality wikis.
Idea: add a checkbox below the blocking option with „downrank similar sites“. Indicate if a site has been downranked in search with a reference to the blocked site.