Google in particular has the data to know what streets are primary routes and what streets are not. Road design and traffic engineering are engineering problems, and shunting high volumes of traffic at roads not engineered appropriately is a bad thing.
By doing this, Waze is creating situations where adequate flow controls (traffic lights, lane markings, crosswalks, signage) are not present and create serious safety problems.
If someone I cared about was injured in this type of situation, I would sue Google, because they have the data to know this is wrong.