I could write a lot about this, but the central issue is that it is very very hard to make changes that sacrifice on-topic-ness for good-ness that don't make the results in general worse. We're working on it though, and I suspect we'll never stop.
I think a lot of the promise lies in as you said, identifying the tangentially related article, or as I like to frame it, bringing more queries into the head. We've launched a lot of changes that do exactly this. (But you are right, it is difficult, and fundamentally so. Language is hard.)