First off, I want to say it's really fucking sad to see Valve just ignoring this issue; it should not be okay for anyone to pose a server as an official Valve one just for potential security reasons, but even more so when it's so overt and when there's so many of them. As far as I can tell, the issue occurs because there's SO MANY of them, that the game just gives up looking for more servers.
That being said, I made a solution last night that uses a cvar in the game to only permit official dedicated servers from Valve being used in matchmaking. Because of this, you never even get matchmade into one of these shitty CN servers so you don't have to worry about disconnecting or retrying over and over until you don't connect to one of them.
Unfortunately, it cannot be a simple Workshop mod. It has to have extra steps because- ironically- Valve has security measures that prevent Workshop mods from executing cvars or .cfg files. So it requires some extra work, sadly.
You can find all the information here: https://steamcommunity.com/sharedfiles/filedetails/?id=3793535875
Please let me know if you encounter any issues and please keep raising awareness of this issue because frankly Valve should be embarrassed that one of their hallmark games is borderline unplayable.