Steemit was clearly meant to be at least a bit like Reddit.  Steemit, Reddit, get it?  Well, in Reddit, when you make a post, you must select one and only one subreddit to post to.  This forces you to think carefully and decide where your post should go, and people will naturally congregate around clearly defined topics.

How well does this work in Reddit?  Well, it's fantastic! Reddit is an amazing site, and I've used it for years as a vital source of news.  So I think this paradigm would serve Steemit well, and most Reddit fans would agree with me.