Is the whole concept of authors publishing their opinions and thoughts on their personal websites dying, or is Google ranking such posts lower?
Google wants to know everything about me so they can serve me better (they claim), but a simple preference to exclude a website from my search results is not possible?
You can. Use "-site:pinterest.com -site:w3schools.com". To facilitate using it in every search, setup a keyword search so you can type "gsearch blah" and have the querystring automatically add those two filters. I agree there should be a way to add sites to a global blacklist in your user settings if you have a Google account. I'm sure Google has monetary reasons for not doing so though.
What do you mean by that, exactly? Is that browser-specific?
In Firefox you can right click most any search bar and "Add a Keyword for this Search".
It used to be that in Chrome it was that easy as well, but now you need to edit a bookmark and it's a bit more involved OR you can add a "Search Engine" and customize the keywords in about:preferences#search
In mainstream browsers at least, I believe it is implemented as an additional field to any bookmark. You change the URL to have "%s" where the search term should go in the URL and then you update the Keyword field of the bookmark.
So, for example, a Youtube bookmark would look like "https://www.youtube.com/results?search_query=%s"
Then when you type the keyword and search, the %s gets replaced with your search phrase. You would need to hardcode the -site: bits to have it always added to your search. You can even create multiple bookmarks that filter out different sites if you want.
Personal Blocklist (by Google)
Blocks domains/hosts from appearing in your Google search results.
I know I have no interest fighting with SEO and I doubt many of the people who host their own small sites do either.