The problem with Paris would be more that it's full of parisians.
It's very cliche, but sadly true. People are smart and educated but undisciplined, behave unresponsibly, and think about rules as mere guidelines. Being "human" and super lenient is mostly a quality, even when it comes to street rules.
Drivers are really bad, bikes don't care about road rules nor surrounding trafic, and pedestrians can strike conversations in the middle of the street if they get to stop the cars around them. There is an intersection in front of a subway station in the town I live, there is a trafic light, mirrors and road marking, and still every two months someone runs through it and gets hit by a car.
I think the best system would be close the streets that already effectively dominated by pedestrians, reserve the most busy streets for professional vehicles (buses, taxi, delivery vans etc.). This would tip the balance to use private cars for very specific reasons only, and switch to public transport for the more casual trips.
Road mortality would be down, people currently wildly circulating on the street would have full areas reserved for them, public transport would have a boost in use justifying more investment in the infrastructure and modernisation, and pro drivers would also have dedicated lanes and streets.
It feels like a clear win for basically everybody.
