Songs of Conquest is a spiritual successor you might be interested in checking out. I agree HoMM3 is still great to revisit and SoC doesn’t quite scratch the exact same itch but it’s a good way to get more of the same but with some variety keeping it fresh
It has lots of modifiers and rules and your hand is a dynamic deck of cards (not just 52 default cards) and so you get the dynamic gameplay and synergizing strategies of a game like Slay the Spire.
If your goal is to achieve realistic looking city streets the best way to do that isn’t an expensive online infrastructure and much more advanced simulation.
If the developers had the skills and time to do that they could more easily have more dense NPC crowds and richer local simulation.
The reason the games aren’t already like that is likely just cost, talent, and target performance, which you’d need a lot more of to execute your plan.