SEO is of course a problem, but it’s been a problem for a long time, and there are ways around it for those who know how to seek information. Proper use of keywords, blacklisting sites with known spam information, searching specific sites, mandating specific words and phrases to be contained in the search etc. It’s true, however, that information has become less discoverable during the latest decade – at least reliable information has.
While AI-written spam articles and such have been a pain sometimes, gatekeeping content is in my opinion as big of a threat to the proper use of search engines for finding information. As more and more sites require you to log in to view the discussion (social media is the worst offender here) much of the search results is unusable. Nowadays the results lead to a paywall or a login wall almost more often than to a proper result, and that makes them almost completely useless. I understand this kind of thing for platforms which pay for creating the content, e.g. news sites, but user-generated content shouldn’t be locked behind a login requirement.
I fear the day StackOverflow and Reddit decide the users’ discussions should be visible for only logged-in users. Reddit has already taken the first steps with limiting “NSFW” content to logged-in users only (on new reddit). Medium articles going behind paywall also caused some headaches a while back.