Categories as they are are a bother to search through. Looking for Pokémon games? Well, look through all these people that have "pokémon" in their names, then all over these streams that might not be for Pokémon!

Categories nesting with Sub-Categories could change this altogether. Let's say we would want to look for Pokémon games. We'd type "Pokémon", head into the "Pokémon" category and look at all the streamers doing different games. If we want some more precision into the category, different sub-categories like "Mystery Dungeon" or "Main Titles" could work, so on and so forth until you reach the "end" of that branch.

This would go like "Pokémon" > "Mystery Dungeon" > "Rescue Team DX", for example.

But the wonderful thing about this, is that it doesn't restrict itself to games.

For example, "Creative", can behave like "Creative" > "Pottery", or "Technology" > "Programming", instead of the smaller tags that people use less (or that don't exist in the first place)!

These kinds of categories could make looking for a particular type of niche that much faster, as well as condense some of the game categories into much more agreeable to see for the viewer, and much more discoverable for the smaller streamer.

You could also check the global interest in single games or whole franchises by sorting them into full nested categories (like "Pokémon", "Zelda", "The Elder Scrolls", "Final Fantasy", for example), or by "individual category", like Twitch usually does.