I think the problem is that such sites are very difficult to find algorithmically, especially when it comes to their poor SEO. The reason they used to be so prevalent in the early 2000s search results is because that's mostly what the web was back then; a bunch of personal websites, blogs, etc.
To do that nowadays would require heavy (manual) curation, which obviously Google isn't interested in.
I don't even think it's that. The issue with older content isn't the search but the sorting. Google and to a lesser extent Bing (and thus DDG) have prioritized content claiming to be more recent relative to the time they were indexed in their display of results.
Showing more recent content is likely generally a safer bet for a search engine. More recent content is less likely to have suffered link rot and covers more recent developments in a subject.
Unfortunately Google et al don't really respect user preferences with respect to sorting. They have a financial incentive to show results they can turn into dollars (or cents).
It especially noticeable to me that just in the last few months, Google has changed their algorithm so some product will be the first item on even the most generic search.
I find it to be utterly terrible for that too.. even when I have verbatim strings from the thing I'm looking for it often simply doesn't show up. ... often because it rewrites the query into something about Kim Kardashian's butt and no amount of quotes or pluses will make it stop.
For the specific context of "I can find something I've already found", yes, it's useful. I just wish there was a way to change that context to "discovery mode" where it uses a different algorithm that is oriented toward finding new information. I want to find sites in the spirit of those old-fashioned sites that are minimally styled with dense information. And not just Wikipedia or a few "trusted" sources like it used to be in earlier times, but a more well-rounded result set.