As for whether a site is tied closely enough to infringement to deserve demotion, the featured article doesn't give the complete algorithm, but it does take into account notices of claimed infringement: "the tech giants have committed to demote websites that have repeatedly been served with copyright infringement notices." I assume these are the same notices of claimed infringement that Google forwards to Lumen Database, particularly those pursuant to 17 USC 512.
That's what worries me. The ones who claim infringement are also those with a monetary reason to restrict others, including those who aren't really infringing but just close to it, and bad for their business.
Until and unless there are serious repercussions for incorrect takedown notices that impacts the one sending the notice as much, relative to their business, as the notice would impact the one hit by it, I see more problems than solutions.
If I made my livelihood on selling sheet music for my own songs, a handful of incorrect takedown notices that bumped me off Google would be devastating to my business, but would have no impact on RIAA/Stemra/ASCAP/Sony, nor the lawyers who work for them.