I don't think that the number of interesting stories have declined, but I think that they have become much harder to find because the number of non-interesting stories have definitely increased. Among the non-interesting stories, I often notice the same usernames over and over. Would limiting the number of story posts per day help the situation?
>>1331+(OP)
Uninteresting stories seem to come either from the same old accounts or from brand new accounts. I'm not sure why brand new accounts aren't banned from submitting stories until they get (say) 100 comment karma.