Far too often I see pedestrians step into the crosswalk in such a way as to make it all but impossible for the left turning car to safely stop.
That's not a real objection.
Competent drivers don't put themselves into that situation. It's the driver's responsibility to be driving at a reasonable speed so they can stop when someone who has the right of way (as in a pedestrian) steps into an intersection. If you can't stop, by definition you're going too fast.