Around 2004/5, it wasn't too big or too diverse. They didn't even have comments at first, much less subreddits. Once comments showed up , I figured "oh well -- now it's no different from slashdot." Of course I was so wrong. I enjoyed coming to the comments after reading the article and seeing lots of interesting commentary.
Right you are that subreddits span quite a spectrum. I chuckle to myself when I overhear conversations about reddit pro/con. It's clear that some people judge reddit by the default front page and they have a very different experience from mine. I've had no thumbnails as the default for probably almost as long as the user preference was available. The combined difference in content and UI between "old" reddit-no-thumbnails-my-subscriptions and new reddit-popular is night and day. It's two vastly different sites.
I can confess to being a part of the problem, though. I started the bad habit of reading the title then the comments and skipping the article. And once imgur appeared, I upvoted the onslaught of mindless memes while never taking the time to consider thoughtful articles. They are after all, the "it" that we have supposedly "redd". I'll put in a plug for /r/TrueReddit - there's often interesting content there.