Re the "just one language" thing, I can imagine I'm not making sense, because I'm not really communicating the context of how irrationally enraged I am over this. The truth is that I only enabled a couple of languages because I was just too angry and frustrated to enable the rest. I know it doesn't make any rational sense, but my reptile brain is telling me that goddammit, Google is not going to make me click on fifty little boxes just to fix them erasing my preferences. Not today. Not this user. There is a part of the brain that is trained to recognize when someone is jerking you around or abusing you, and when it gets triggered inappropriately, it is impossible to turn off. (I'm sure anyone who has worked in customer service will recognize what I'm talking about. Right now I am the bug-eyed paranoid who is convinced they are intentionally screwing with me for their own amusement.) So long story short, yes, it seems immensely important to me that I have to check fifty boxes instead of one, and I still don't have my unfiltered search results, not until I calm down enough to go click on all those boxes.
As for the problem of change, I can sympathize with the problem they face. I'm sure that globally minimizing user confusion and frustration is one of their goals. As for me personally, they'll have to count me in the "used the product incorrectly for years without realizing it and is now very angry about it" category.
UPDATE: EVEN ANGRIER:
So I swallowed my pride and went to work clicking.
"The page at https://www.google.com says:
The number of language restrictions is limited to 8, so only 8 of the languages selected will be saved."
That doesn't bode well. But then: "The page at https://www.google.com says:
Your preferences have been saved"
Ah, but guess which time it was lying :-/
So unless there's another way to turn off language filtering, Google will filter out every language besides your primary language and seven others. (Yeah, your interface language counts as one of the eight.)
That's terrible. Even without Google Translate, I swear I got useful information from a page in Polish once. Plus there are pictures, video, miscategorized pages, mixed-language pages (what happens with those?) and the simple coolness of finding out that someone in Vietnam is using an open-source library you committed a patch to. And of course, Google freakin' Translate! Unless Google is translating every single page it crawls. Which it might be -- that's something to think about. But it does very poorly with some pairs of languages, and if it filters out every term it can't translate, then it will tend to filter out commands and symbols. And here I am speculating about how it works again, which goes back to my original point.
With my track record today, I'm sure I'll find out I'm misinterpreting this somehow, but I'm starting to feel a little bit justified in my anger. Ah, I can't lie. I feel much less angry now that I feel like less of a fool :-)