Medicine researching on the internets always was among the hardest topics. And anyone who really understands Medicine has to write on any advice not to consider it as a real medical advice... I agree that google has degraded down to unusable in comparison to non-global searchable websites (like SO) but Medicine is very bad example to your point.
In fact, I wonder how far a search engine could go with a curated list of "good actors" you exclusively serve up results from. Add a "search everywhere" link for people that prefer SEO hell.
When Google started, the web was honest and innocent. People linked to the pages they liked, and Google could crowd source those links and raise up the most popular pages.
Now most of the web is lies meant to confuse search engines. Figuring out what pages are good is no longer a feasible task for software.
Of course it is. It shouldn't be at all difficult to train a large natural language AI model on SEO spam pages. But nobody will do it unless they can figure out a business model that makes it pay.
Or a non-profit organization is formed to do search spidering for the benefit of the whole world, much like Wikipedia or PBS.
At this point, it's no different than an appstore in terms of volume. Ironically that's where we're heading with most websites being "3.0" and just SPAs and now PWAs even.
I cannot imagine it being easy, but I find it hard to believe that Google aren't able to weed out the worst offenders. For a large number of queries the results are all SEO spam. Try searching for anything related to health and get a useful result. It's no longer possible.