I don't think it's clear at all. For someone who visits the site without participating (for example to read an answer that showed up in a Google search), they see a bunch of good answers. That looks like a high quality site. Edited to add: And if their question was asked and deleted because it was considered "bad", it never shows up in a Google search.

You can't say the mod culture is not improving the quality of the site because you haven't provided the original content without moderation to see what it looks like.