This seems to be a Google-specific problem.
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Example that I just double-checked: (I don't claim any political views here; JUST an example)
Reddit's largest subreddit for a political candidate is r/The_Donald. Objectively, a rather popular site.
Google (with or without SafeSearch) returns zero results for "Reddit The_Donald" linking to the subreddit. [1] It's only results are indirect discussions about the subreddit.
Whereas DuckDuckGo, Bing, and Yahoo show the subreddit itself as the very first result. [2] [3] [4] (https://np.reddit.com/r/The_Donald/ which is Reddit's public non-logged in site.)
So Google won't display a high-traffic site. I can only assume they find the content objectionable and so will not link directly to it. I understand how some may want that, but that's not a simply not a service I want my search engine to perform, especially when SafeSearch is disabled.
[1] https://www.google.com/search?q=Reddit+The_Donald
[2] https://duckduckgo.com/?q=Reddit+The_Donald