I think your first conclusion is wrong. From what I have seen, Stack Overflow appears to be fairly well-supplied with quality posters, but they just don't have

I think your first conclusion is wrong. From what I have seen, Stack Overflow appears to be fairly well-supplied with quality posters, but they just don't have as many questions as the "plz email teh codez" crowd. The problem isn't that good questions are generally going unanswered, and it isn't even that good and novel questions are in short supply, but that there aren't as many good questions and they're having trouble stemming the tide of bad questions. The disproportionate rise of bad questions is the core problem.