Grids are bad for cars because four way stops are really inefficient at processing them. You'll notice in American suburban planning that there are as few four-way stops as possible inside a subdivision.
Non-grids extend the distance of a lot of trips and are thus hostile to slower non-motorized users. Driving an extra 500m is not a big deal for a car but is an additional several minutes for slower users. And non-grids in the US funnel onto very big roads with few crosswalks, so that's even more diversion distance; and then on top of that it can easily take a few minutes to even get a walk/cycle signal at an intersection.
In contrast it's very easy to make a grid less hospitable to cars but also still allow pedestrians and cyclists to take the shortest path; just lay bollards diagonally across an four-way intersection that are too narrow for vehicles but large enough for bikes and people.