Why is it in the idle category? It's as idle as a typical RTS: You can idle, but you'll lose if you do it.
We've tried creating a combination between the classic city builders, idle games and civ managers into one as part of the GMTK2024 game jam, but we've unfortunately ran out of time in the balancing department.. so it ended up requiring too much interaction to be an idle game, but also too slow paced for a city builder :D