Cities: Skylines

Performance aside it just wasn't ready for release anyway. There are major bugs in its simulation in the economy where stuff like your cargo ports don't function and commercial isn't actually using your production products and are just faking it. The performance issues are made worse by them not implementing proper LOD when you zoom out so that everything still has way too much detail in it's models that you don't need.

I love the game but it needed like 6 months more development and testing before it should have even seen the light of day as an early access game at least.