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.
For me the majority isn’t even relevant, I’m on Twitter specifically to follow certain people or organisations which are related to my interests. I barely use Twitter these days but most of the accounts I follow are still on Twitter and bascially nobody is active on Mastodon (or any other alternative I can access for that matter).
I love the idea of Mastodon, but it’s worthless to me if my timeline is empty. Lemmy and Kbin are different because they’re organised around topics instead of people.