I’m going to preface this with this computer will last quite a while, but you won’t have nearly as much of an upgrade path if you went with an AM5 platform (latest AMD CPU socket) on DDR5 (latest generation of RAM). With that said, your use case seems to be one that will not require keeping up with the latest games, so if you want to save some money this is what I would do.
NOTE: Prices are from Amazon, you can likely find a few components cheaper elsewhere.
CPU: You don’t need an R5 7600. I was running an R5 3600 up until a few months ago and the only reason I upgraded was I found a 5800X3D for a good price. I’d go for an R5 5600X which is $60 cheaper than the 7600 and will be more than enough for City Skylines 2
Motherboard: You can now get a B450DS3H board for that CPU for $40 cheaper
RAM: You’ll now be on DDR4. Get a 16GB kit of CL16 DDR4, will be about the same price as the DDR5 you have. May want to go for 32GB of RAM because sim games eat RAM, but ultimately up to you. You can always buy more down the road if needed as a 32GB kit is like $5 less than 2 16GB kits.
Case: The no-name brand cases on Amazon are actually quite good. You can get a nice case for ~$50. Hell, I just found a Thermaltake Versa H18 for that price. Another $55 saved.
GPU: I haven’t kept up to date on GPUs, but I’ve heard good things about the 6700XT, and benchmarks look respectable for BG3 and City Skylines 2. You could likely get away with something a bit less powerful, but price to performance seems to side with the 6700XT.
This brings the price down to $831. You could ditch the aftermarket cooler and get it under $800 as the 5600X comes with a cooler, but I’m never going to knock aftermarket coolers as they tend to be much quieter and less whiny than stock.