everybody who's been on usenet for a nontrivial amount of time has experienced exactly what you describe, several times. expecting reddit to be different is like hoping for world peace. you should instead assume that degradation of quality will naturally happen as a community forum becomes more popular and either introduce moderation or fork off a smaller forum... and both of those happen, as you noticed.

this comment may be misplaced, but i've finally entered rant mode after reading the 5th or so comment saying "reddit is popular hence degrades" and misses (or stops short of) the point that all communities degrade with increase of their popularity - every now and then somebody writes that hacker news is not what it used to be.