If you replace “cities” with “rural towns” you might have a better understanding of why we still need cars in regional areas.
Australia is HUGE, the rural towns are far apart and have low populations.
You can’t run a bus/train every 10-20mins for 3 people, you run a bus/train ever 2hrs for 40 people, and they’ll never change.
I’m all for accessible cities, for those that want to live in them, but you’ll never get me away from my quiet rural life on the edge of regional centre. The reality is the transport in my town of 40,000 people has an insignificant impact on the environment compared Sydney, for example, with +5,000,000 people.