No urbanization is sustainable. You can not build cities without eating forests. The forest may already be gone where the city is sprouting, but it just means someone else’s forest will be stolen and destroyed. Forests are also critical for the management of stormwater and their disappearance even hundreds of miles upstream, exacerbates flooding issues in cities.
The issue of economic growth is also an important one. GDP growth on a planetary basis is down, and due to ecological collapse and growing inequality the rate will stay low. Developing countries will grow faster than old industrial countries, but with climate change and ecological collapse, the growing cities are in for tough sledding., and can not count on economic growth to pay for the infrastructure they need. What cities need to think about in developing sustainably is how to grow enough food, and how to be resilient in the face of climate change and re3source shortages. Most of what I see by cities is skirting around the margins, They are too beholden to real estate speculation to mange the land and development properly. They are faking sustainability. i know mine is and it claims to be a leader.