Driving constantly in just stop and go traffic isn't the best thing for your car but it's not a terrible thing either.
Cars are made to drive whether in stop or go traffic or on the highway.
However when you're just driving in stop and go traffic and not getting your vehicles engine up to temperature then you can get condensation in your vehicles engine oil through the natural combustion process.
That then can lead to milky oil but when you drive at highway speeds then the oil should go back to it's normal color and the water and moisture should be evaporated.
You put more wear and tear on your vehicle driving in stop and go traffic and actually when you put highway miles on the car it's much better than just putting less stop and go driving miles on the vehicle.
Whether you go to far your engine is still idling so the engine is getting wear and tear on it over the time and the air when going down the highway also helps to keep your cars engine cooler as well.