Cars are by now a hard to reverse environmental and urban planning disaster across the world. We are stuck with them. As a mode of transport it has grown uncontrollably at the expense of all others (except the airplane) and practically everything has been shaped to accomodate it.
Reversing that development, limiting car traffic to where its really needed is like trying to perform a complete heart and arteries transplant on a living person. Even if there was a will (which there is not) it is not clear if there is a way.
In the best scenario it will be an excruciatingly long transformation (~50 yr) as car oriented cities (or city sections) get slowly deprecated and the car-free or car-lite segments become more desirable, more livable.
You still need vans and trucks delivering stuff to people and businesses. Bus is far more flexible form of transport than tram. Just... if you need to wait ages for one and there is no stop nearby nobody will want to wait.
That's mostly a chicken-egg problem, if more people rode the bus there would be way more frequent stops and more nearby ones.