Almost all cities move in the opposite direction. The expansion is not bad, but if they are not doing it with planning, in the future Shanghai will look exactly like the old Aztec cities. Wonders of the time, abandoned because of the lack of usable services.

The real issue here is the mentality, I see it in your thought "so that even if the city centre is 50 km away, we can get there in 15 minutes." - The main idea is to make the city center a want-to attraction and not a must-reach. Anything that you would need from the city center would be right where you are, in other plazas, under 20 minutes of walk time.
You would just visit the center if that is where you and your friends want to go or as a tourist attraction, but not because it is mandatory and the only one for cultural or social events.

It's not your fault, it's the city planners and it's the lack of involvement. And the Chinese have evolved a lot in these last 10 years.

https://www.ted.com/talks/peter_calthorpe_7_principles_for_building_better_cities?utm_campaign=tedspread&utm_medium=referral&utm_source=tedcomshare