I...have walked around the less nice parts of Paris? I'm not sure what your point is. In the less nice parts of Paris, the noisy areas are still mostly the areas with busy roads. It's simply the biggest source of noise pollution in cities and I haven't found anything that comes close. Maybe in specific areas you can find people playing obnoxiously loud music with helicopters buzzing over constantly but that's certainly a very specific and hopefully rare set of circumstances. The same with yelling and crime and so on. If that's the default in your city I'd agree you have vastly greater problems than the sound of cars.

Not much a problem in my city, but those which I've been to that are seen as "walkable" and with a "vibrant city life". Essentially all places with considerable tourist traffic.

Paris is very densely populated - I'm surprised anyone attempts to drive there, because at these densities and distance between buildings it must be horrible.

My point is: it's not that clear cut. Removing cars is what makes places like Paris bearable, but the problem lies in the sheer population density that a truly walkable city over a certain scale requires.

I moved to a city that has 2/3 the population density of my previous location and even though it's just swamped with traffic, it's actually quieter on average.

I feel like population density is completely left out of the conversation. From my experience there's a middle ground between car-oriented suburbs and human pile-ups like Paris(or other cities approaching this density) which is rarely explored.

I certainly would agree that Paris isn't an ideal city. My experience has been that cities with 1-2 million inhabitants with reasonable, but not extreme, density (i.e. much denser than suburbia but less dense than Paris) have been the most pleasant.