yes, full and clean uninstall would be the way to go, no reinstall, no repair install or "verify game files" and all that stuff.
Then manually check the "usual suspects" like "app data/roaming" on your c:drive and of course the steam game library folder(s) for any remains.
For the fresh install I would even recommend to chose a new folder name, just to "kill" any existing path references that might have been overlooked.
edit:
ah I just saw zztong edited in his post that he was able to reproduce the hangup with the "no towns" setting on his side too.
So it IS a bug in the end?
Funny somewhat, like the game tries to "draw" at least one road, but it can't because with no towns there's no points to connect the ends with.
Well you could say the game is smarter than some construction authorities 😄