Allow nesting of Categories and Sub-categories.
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.
I had this exact same idea--I also find it a little silly that HD remasters are sometimes separated from their original games. I don't really care if anyone is playing, say, Skyward Sword HD or the original Wii version; the gameplay itself is almost identical. I just looked right now, and if you search up the category "Pokemon Sword/Shield," there are many streamers playing other games in the series but who are mis-categorizing their stream as Sword/Shield, presumably intentionally so they have a higher chance of being discovered. It would seem in this case, the "Pokemon Sword/Shield" category is already being awkwardly used for this purpose, which clutters the experience for those who really are just looking for streamers playing Sword or Shield. Doing this in conjunction with tag filters could be great-- if I want to see someone speedrun a Pokemon game--any Pokemon game-- I could just look at the "Pokemon" category and filter using the "Speedrun" tag, instead of searching every Pokemon game I can think of and filtering by that tag there.
Fantastic idea, love it!