I remember being in Japan and seeing these "all walk" signals, including crosswalks that went diagonally through the intersections. Brilliant.

I fully agree. I had two situations in the past 2 years where cars almost ran into me (as a pedestrian) doing a left turn, with screeching tires just barely avoiding me. In both of these cases I probably got out without an accident because I expect drivers to be idiots and was careful enough to act accordingly.

You summed it up when you said you expect drivers to be idiots. This is what I teach my kids. I say the cross walk does not mean a thing. One person looking at their phone and you are dead in the cross walk. I always tell them look and keep looking and expect that even if the car in front stopped be ready for the car behind him to hit him and push him into you (something that I’ve had happen personally).

The crosswalk's only purpose is to determine who pays for your funeral.