To be fair, w3schools and the like don't just copy content. They provide different information and, most importantly, present it differently from official docs. And for many, their way of presenting information may work better.

I acknowledge your opinion but still do not want to see that and several other spam sites over more official sources such as mdn.

The W3schools hate is a bit outdated. Even W3Fools[1] eventually backtracked and acknowledged that W3Schools has continuously improved and updated their content.

1. https://www.w3fools.com/

This is such an easy optimization that Google has to have tried it and seen their ad revenue fall.

"Permanently remove this site from search results" seems like the absolute easiest "personalization" to implement.

And the most certain too. You don't need to guess whether or not the user really needs that result

But what will Google do if users end up banning the majority of websites with Google Ads and/or analytics?

The reason Google doesn't fight SEO spam (and just generally annoying/obnoxious behavior such as paywalls) more aggressively is because it doesn't want to bite the hand that feeds - all these spammy sites have ads or analytics that benefit Google.