Examples:
- utility services: I keep having problems with e.g. ambulances or trash collectors that are spawned very very far from the area where they're actually needed, even if a hospital or incinerator is just around the corner.
- size of buildings: I don't like the approach of having tall buildings / high-rise in developed high-value zones by default. In my opinion the size of a building should mirror only the density of the population living in that particular area, so it should be possible to have as well tall buildings in low-value zones. As well the amount of people living in tall buildings is for my taste not a lot different from the one of med/low-buildings, taking into consideration the height of the building... => how tall is a building should be a function of the people inhabiting it and not related to the value of the zone.
- deaths/births waves: once my cities got big, I kept getting each time waves of people dying and later a lot of births. There is a plugin that fixes this, but this should really be part of the basic game.
- traffic: this is actually already working veeeery well on multiple levels (e.g. very nice/interesting to observe how queues generate - I can observe that for hours hehe) but I do miss a logic that says e.g. "if this section of street has during a certain timespan ~95% of space occupied by vehicles then assume that there is a queue => mark that section of street temporarily non-existing for non-involved vehicles so that other cars would start looking for alternative paths" or something similar.
All in all, even if Cities Skylines was already a giant leap compared to the classical Simcity-games (excluding the last one which was just horrible), I'd definitely like more "action=>reaction"/"cause=>effect" in a potential future "Cities Skylines 2" or in this case in "CityBound".
Cheers
EDIT: for more details search in this page for the post containing "Unfortunately, traffic management is the only part of the game that really holds up as a simulator" by "amyjess" - I just read it now and I think that I agree as well with all what's mentioned there about CS (but I honestly don't rememember anymore how Simcity4 worked...).