If you use Greasemonkey / Tampermonkey, etc. you might want to check out 'Google hit Hider by domain'[0] [in spite of the name, it works on several search engines, not just Google]. It provides a really simple interface to ban [with various levels of extreme prejudice] sites from ever again appearing in your search results.

[0] https://greasyfork.org/en/scripts/1682-google-hit-hider-by-d...