Well, the "good" content is defined by what community value.
By increasing the size of the community, you dilute the quality variable to the most common denominator : meme and cheap giggles.
Even with only 4 posts/day, if there is enough shitposters & shitlikers, the top post are gonna be shit.
For the downvote bot and flagging system, I don't know. I guess, if there's enough counter-weight from people liking shitposts, their utility is reduced. (But I could be completely wrong, I may need to lurk more before talking rubbish)