If you want to discuss the launcher, please do so here: https://steamcommunity.com/app/255710/discussions/0/1742265315845302132/
Hmm, that sounds like a new error. Try verifying game files by going to the library in Steam, right clicking on Cities: Skylines, select Properties, go to the tab named Local Files and click on Verify Integrity of Game Files. Let Steam do its thing and start the game again.
If you have errors again, upload the log again and drop a new link, so we can see if something has changed.