The biggest issue is that people still think of reddit as a single community. It's not, and you can't stereotype all of reddit by looking at /r/pics and /r/politics. You have control over your home page and can remove noisy subreddits from it.
I addressed this in my comment. I am aware that each individual user controls their own reddit, my problem is it is very difficult to find good relevant subreddits without relying on third party tools (which very few users are aware exist) or randomly stumbling upon subreddits through comments or cross posts. If there was a reddit system that could match my voting preferences to specific subreddits (for example if I upvote Minecraft content in r/gaming it recommends r/minecraft) the quality of the site for each individual user would increase. If the quality of each individuals reddit experience increased the entire site would improve.
I agree that a recommendation system would be awesome but is it really that hard to find a new subreddit? The search feature at http://www.reddit.com/reddits/ seems fine.
The r/gaming example is a perfect example of why a search system doesn't solve the problem. I'm already subscribed to r/gaming so I don't think I need to search for another gaming subreddit. Another example would be r/battlestations, a subreddit for people to post their desks, I would never think to search for "battlestations" but it's a subreddit that I like a subscribe to (which I only found because someone recommended it elsewhere on reddit).
Search only helps you find what you're looking for, it doesn't help you find things you might be interested in.
The reason you wouldn't think to search for "battlestations" is presumably because you don't visit 4chan. That entire subreddit is actually an example of a part of 4chan leaking onto Reddit.
