I've been thinking about this for some time as well, but writing a quality post takes more time than I currently have available.
The help I can offer, however, is the perspective of someone active in low-traffic tags. My feeling is, there aren't as many people from those tags on meta, compared to e.g. python or web development areas.
What makes Stackoverflow useful for me is that I save time. For basically any objective, on-topic question that multiple programmers face, there's one or more Q&As. We have the close reasons to remove questions that don't meet this criteria. Cleanup, in the best case results in a canonical Q&A, either by editing or posting a new question. For the tags I'm on, this doesn't really work. There are a few popular questions, but they aren't put in shape. But they still help people, because they contain some answer, often from experts on the topic. Only, those experts sometimes don't want to spend their time to make the Q&A shine, and not many others do so. Also the author of the question is often long-gone.
So we ended up with lots of "useful to a handful of people, but not very polished" questions.
Fixing them in the current landscape is often impossible because of three main reasons:
- Few people vote on them
- We discourage edits that "change the authors intent"
- The question is (close to being) off-topic
I'll ignore 1., because the company already has its own agenda. Still, up and down voting is viable curation, of course.
For 2., I think we could be a bit more lenient, especially for questions. I'm not sure, though, how to achieve this without creating chaos. Existing voting has taken place on the existing answer. Major changes decrease, how much I can rely on a post's score. Still, I believe if done carefully, this will improve the site. Many of the top voted questions have very little resemblance to their original form. To me, I don't care if the author asked "X". If thousands more people find a solution for "Y" in a question, than to "X", the question should be about solving "Y". Alternatively, the issue could be handled by better meta data on posts, as suggested by TylerH in the comments.
For 3. I see the rationale to clean up. However, I consider myself lucky that many tags haven't been cleaned up, because I rather have an off-topic answer than having no answer at all. I know I won't win anyone over to keep those questions, but if we decide on more aggressive off-topic closing, I hope to see a way to preserve the knowledge. Migrations are not the solution, because they are blocked after 60 days and the process doesn't scale (AFAIK, there's e.g. no queue for migrated questions). Not sure how to find a balance here.