Before the expansion packs, topics and genre made sense. Example a action military game could be a first person shooter or 3rd person. Possibly both. It was left up to your imagination. Them expansions offered stuff like parckour and kittens -_- then some added1st person shooter and 3rd person shooter. Not exactly a topic but couple that with military it made sense. This could be changed with two topics sure but then when you add modern to the mix it changes things. Have like a military theme with modern 1st person shooter and you get a very specific game. Now obviously you put action or simulator but what if you make if. RPG sci fi 3rd person shooter open world. Then you got mass effect. I feel things like medieval and fantasy are also themes. Sports is a theme but basketball and football would be a topic.
I know this would make things more complicated to create games and design combos around. But it also helps make very spefic games. Is something like this even possible to add in? I see some crazy stuff people are adding in like camelots ambition. Maybe have two combos like theme and genre are one, the have theme and topic be a different one. So pretty much theme and genre still act as normal but have topic give a bonus to quality of the game maybe? So it makes it easier to do horrible combos like strategy sports and making a good theme/topic combo by putting in football and manager as topics, make it a good theme/genre combo. Should also make it easier to get higher grade games but not overly easy where you can make any game with a good topic theme. This way your games can have variety and come out closer to how you imagine them.