If you blacklist them just for yourself, the sites don't care, no economic impact. If Google does the same, they'll work around. There's lots of spam-only sites, but they also often cleverly avoid detecting by mixing in content ranked as valuable/legit. SEO also certainly "attacked" otherwise legitimate sites like Reddit, although what GEO is doing there is far worse I imagine.
Sure. It probably works better in isolation.
But there seemed to be some time lag for a SEO spam sites to climb. Removing the ones that make it would mess up the economics at the time. Like the Stack Overflow mirror sites or like spam phone number pages with no other information but the number.
And I guess plenty of search queries would have no moderation. But I mean I spent like 10 minutes. You could have 10 FTE doing that.