Is there any value of ensuring the site retains only answerable questions, and if a question is in fact answerable, is it the responsibility of the community or the moderators to find these questions and promote them? Many answerable questions are in the fullness of time buried due to lack of activity. I wonder how these are found and handled. I as a user get notifications for first posts, edits, potentially low quality posts, etc. but nothing says "oh hey this post has sat for 5 years and no one has interacted with it." I mostly find these posts by accident if, say, I browse a users history or an obscure tag.
The primary mechanism is voting: vote up the questions you come across or look for that are useful & clear, vote down the ones that aren't; if enough people do this, someone searching for questions to answer in an area they're knowledgeable about will easily be able to find the worthwhile ones.