How hard would it be to assign websites an actual reputation again?

Include ads on the destination website as part of the reputation score. If a website is loaded with ads, sink it to the bottom. Google doesn't do this because they likely make money from the ads.

Heuristically determine spammy content. It's pretty easy to tell at first glance which content is bullshit, so it's probably not hard to create an ML model to do the same classification.

Manually assign positive weights to websites used by engineers and domain experts. You could even curate this list in the open and solicit help in maintaining it.