I loved the SimCity series, so you'd think that Cities: Skylines would have appealed to me, but it's always felt frustrating, which I attribute to a few core issues:
- Agent-based simulation instead of model-based (the latter is what the Maxis games used). Agent-based simulation is performance-intensive, and in practice it led to all sorts of gamebreaking bugs. Last I checked, the game still caused traffic jams because every car would enter the turning lane immediately. It also causes the infamous death waves. Some of these are hard to fix without changing the core simulation model. Some of these would be trivial to patch, and it's kind of embarrassing that they haven't.
- The DLC is essentially mandatory, in that they release updates to the free game alongside every DLC, and the free updates introduce some of the features but not all, and they end up breaking the balance of the game unless you purchase the full DLC.
- The game is far too easy, unrealistically so. Even on the harder difficulty setting, it's just way too easy to create a cash cow and create the optimal city without any real challenge.
Cities:Skylines is good in sandbox mode, if you want to create beautiful-looking models of cities. Which is a valid use case and there's definitely a market for that. But for people who like the original SimCity games and enjoy simulations, it's... just not that. There's a reason that professional city planners used the original SimCity games as tools for study and development, and that's what made (for example) SimCity 4 Rush Hour so much fun to play.
Whenever I want to play a citybuilder, I end up going for Factorio, Oxygen Not Included, or Rimworld. None of those are citybuilders, but they're the closest thing I've found to substitute for what made SimCity games enjoyable that Cities:Skylines lacks.