We're doing a lot of thinking right now about how we can make topics more useful.
I don't have a firm answer for you, but my advice is to not overthink it. If you're interested in something, chances are there are more people out there who are also interested in that thing. They may not be on Cake yet, so it could take some time and effort to find them and bring them here, but they're out there somewhere.
So I think your best bet is to start conversations about the stuff you're interested in and spread the word and trust that people will find them eventually. Hopefully sooner rather than later. 🙂