I agree with you that redditors as users should curate the site towards their own interests, but I feel that the overarching "community" of reddit often spreads towards smaller communities as they grow and their moderators choose not to moderate on a rule of content.
Some subreddits have stayed wonderfully on-topic and full of great content such as the safe-for-work porn network (/r/earthporn, etc), askscience, and others, but they usually require heavy or automated moderation to stay this way. I am fine with this, and if all subreddits could preserve their own standards of quality, I don't think anyone would be complaining about reddit save for the laziest of users.
On the other hand, most subreddits end up becoming similar to the cheap and digestible content akin to that of the front page of reddit. There's nothing wrong with this content. Lots of people like it and they have all the right to enjoy it and share it. The problem is that the people who enjoy this content outnumber those who lean towards richer discussion, articles, and news, and as subreddits are often mostly democratic, this means that users who have already invested the time in finding subreddits they like have to do so again.
One example I like to use is /r/skyrim. Up until a month before the release of the game, the subreddit had less than 30,000 users, and the majority of content included articles about the game, predictions of game mechanics, and discussion of lore throughout the Scrolls series. Just 6 weeks later, the subreddit was indistinguishable from /r/gaming except for the fact that all of the content was focused on the game Skyrim, and the userbase had (if I recall correctly) tripled in size.
Maybe my interests don't fit with the content I'm seeking, but I really dislike how so many communities on reddit that I've enjoyed have changed for the worse (in my opinion). There's still a number of places on reddit that keep me coming back, for now, but I don't agree that the entirety of complaining about reddit is due to the front page, just most of it.