Personal blogs, passion sites filled with resources where they might sell a couple products, open source resources built by a community, etc.
I can say its almost rare I get the answer I need on a commercial platform besides reddit, but that's only because reddit replaced forums where ads were generally small and unobtrusive.
Yes! I would say 90% of the useful stuff I find on the web is this sort of site.
YES. Not only would I find more pleasant sites, but they'd likely be of higher information quality.
Of course Google's business is those ads, so they cannot fix the problem. They are the problem. Google's raison d'être is spam, so of course they're going to return a bunch of spam to you. Same deal with email. I get plenty of spam to my gmail inbox with things like, literally, "THIS MESSAGE CONTAINS ADVERTISING". Obviously, Google is not even slightly trying to filter spam from emails, even the spam that labels itself as such.