Useful and/or somewhat serious subreddit can have submissions derailed and useful content buried by meme comments, and meme subreddit can have someone be too serious and upset or disheartened when people don't engage on what they see as an important or cool thing (or not even that people don't engage, but that any discussion is derailed by the community as a norm).
It's great that I can go to one place for almost anything (kind of, they're getting a little pushy and scummy with the monetization), but sometimes the community is also a downside.