Yes, they're serious. The problem isn't that some cars exist, it's car dependency. Car infrastructure is inefficient, expensive and takes up enormous amounts of space. It's also ugly and loud. Cities built around cars get very spread out, so walking, cycling or public transport become inefficient or unsafe options. As a result, you have to drive, whether you want to or not. If you want to go literally anywhere, you have to get into your car and deal with traffic. But it doesn't have to be that way. Cities built around walkability, cycling and public transport are not only more efficient, but also much more pleasant, even for those who still want to or have to drive. Good alternatives to cars are the only way to really improve traffic. The idea isn't to just get rid of all cars but to make it so you don't need one.

If you want to learn more about good urban planning, check out the excellent YouTube channel Not Just Bikes to get much better explanations of these concepts. I especially recommend the series about Strong Towns as an introduction.