Earlier quoted context omitted.
>As long as safety for people is not prioritized over car speed It’s possible to have both. It’s why we have grade separation. https://en.wikipedia.org/wiki/Grade_separation
It's prohibitively expensive, better would be to sacrifice some city corridors as pedestrian only. Cars don't need to be in the city centre on every street. Most pedestrian friendly streets that do mix in cars actually do the opposite to grade separation, slow down the cars a lot and make it clear that they are in a pedestrian space by removing demarcation between cars and people,which changes behavior.
My city introduced car free streets, then they introduced mall cops to them and they effectively became unwelcoming commercial strip malls. America has an America problem, and the solution won't be simple.