Busses and delivery trucks are the most noisy and polluting! That doesn’t seem like the panacea you suggest.
Once private cars are off the road, busses and trucks would spend less time in traffic. That increases their economic yield, which in turn, makes a gradual electrification mandate economically feasible.
2. As for carrying, based on my experience of living in a walkable neighbourhood where thousands of people lived within a kilometer of the central shopping area, a lot of people would bring carts that they would push their groceries home in. If you can push a small wheeled grocery cart through the total 100 meter aisles of the grocery store, then you can push a big wheeled cart the 1000 meter to your house on the sidewalk. Given that I often saw 80 year olds doing that, most healthy people should also be able to do it, no problem.
Buss volume scales with funding and political will with upfront costs and delayed realized benefits. Generally supply is outstripped by demand.
Personal conveyance volume does not appear to have any of these limiting factors. And has terrible demonstrated density.
https://www.iwillride.org/what-200-people-look-like-driving-...