If they're afraid that a mall will create traffic bottlenecks, maybe build those malls so they're easy to reach on foot, by bike, or with public transport. That way you don't get that traffic bottleneck.
People buy shopping carts worth of stuff at malls. That's not exactly easy to schlep on a bike or a bus for most people especially if you are in poor shape. A lot of people in the U.S. today live in walkable areas, but opt to just take a climate controlled car with a spacious trunk 5 mins to the grocery store vs walk 15 minutes one way and back with 25 pounds of groceries in poor weather.
If shops are nearby, you go more often for a quick trip to the shop and buy much less. Lots of Dutch people go shopping on their bike, and that works perfectly fine. And people who really buy a lot, walk home with two big shopping bags. That works too. It has never been a big problem here.