In my niche, for many keyword variations, I see sites that are really old, late 90s, ranking on the first page. Never ever saw those sites before.
All of those sites have very low Alexa rank. Sites with static HTML content. Low quality content.
These old sites never really received much traffic from Google over the years, Google doesn't have any negative data attached to those sites, so they rank well. The sites that received lot of traffic from Google, those sites have negative factors attached to them, like high bounce rate, old content. Users would bounce off those low quality sites, and Google would record that, just a matter of time until those sites drop in rankings. I wonder why is Google taking so long to fix the serps.