LarryNG All search engines do pick and choose, which they often should, but I hope that DDG picks and chooses wisely.
I understand the DDG (which I don't use) bases rankings on Bing (which I do use) rankings. Bing search strikes me as reliable and unbiased, and I use it exclusively.
LarryNG Google uses and admits to using millions and billions of existing websites' data to be the judge of whether a web page's content is accurate (I'd have to dig through my files to get the original Google souce, but I suspect that it is still findable online under the keywords of "Google truther"). The result is 'science by popular opinion'.
I don't know the current criteria for any of the search engines, but I don't have a problem with search rankings based on "the great mentioner", that is, search engines raising the ranking of specific articles based on the number of times that a particular article is linked to on sites with recognized expertise in the field. However imperfect the process might be in actualization, "the great mentioner" increases visibility of specific articles of merit on otherwise obscure websites to a higher prominence in the rankings. I understand the "science by popularity" argument, and recognize the dangers, but "science by popularity" also translates into "cream rises".
LarryNG Often, if a website has fresh authoritative information of scientific topics (or even old-school physics), Google will block the web page as well as all or a portion of the website itself if the new information does not agree with popular 'socially approved' opinions
This is the obverse of "the great mentioner". A scientific article, however original and brilliant, is not going to get traction if it is posted on The Flat Earth Society's website. As my mother used to tell me when cautioning me about a couple of my wilder friends, "You are known by the company you keep."
In all of this, I think that it is important to keep in mind that search engines do not do "peer review". In fact, I'd be surprised if anyone actually reads/reviews any of the ranked articles. The algorithms and cut-off criteria are automated approximations of "peer review", and are, accordingly, imprecise. Cream does not always rise, and almost certainly will not rise if mixed in with muck.
I draw the line at search engine censorship, however. My view is that speech should not be abraded, that the marketplace of ideas will, eventually, separate the wheat from the chaff.
I recognize that uncensored speech can be dangerous. The marked rise of anti-Semitic attacks in my country over the last several years is a direct and inevitable result of the rise in verbal attacks on "international bankers", "globalists" and "rootless cosmopolitans" (code-words for Jews) rising at the extremes of both left and right. As Rabbi Abraham Herschel observed, "Speech has power. Words do not fade. What starts out as a sound, ends in a deed.” Speech always comes at a price, and the price is usually not paid by the speaker.
As a result, well-intentioned people often support efforts to censor the worst speech. But all in all, I think that uncensored speech is a critical element of a free society. I do not think that search engines should be censoring content, however heinous or inaccurate the content may be, and regardless of consequence to life and property, unless the content rises to the level of shouting "Fire!" in a crowded theater. Limits must exist, of course, but the limits should be exercised only in the most extreme cases.