Ouch. I have no experience with the digital version of New York (the real life one I am quite familiar with), but I have tested out custom worlds with breaks in the world lot/road routing as described and with or without CC they are impossible to play for very long. After a while half of the residents cannot leave their houses as said because they are unable to route across town and the game performance goes down to zero as it constantly tries to reroute everyone. Those who do make it out of their houses get stuck halfway to where they were going and end up on the sides of the roads waving their arms and screaming at the player.
Even if really only totally engaged with the sims under active control and if one finds creative ways to get past the broken routing for ourselves (break trips up into three smaller parts to bypass the broken intersections for example), and even if we don't notice what the other residents of the world are doing, the game quickly becomes not very much fun to play in worlds with such routing flaws built in.