Earlier quoted context omitted.
In theory, an unprotected left should be easier for software than a human. The issue with them for humans is that there are too many places traffic (and pedestrians) can come from. For computers, once you solve the problem of seeing traffic coming from one direction, Nx the computing power can see traffic coming from N directions. The problem Tesla has is that they still can't do basic things reliably enough
Human drivers are also impatient, distractible, poor at judging speed, and have visual blind spots. But a big problem with a lot of unprotected lefts is poor visibility of oncoming traffic. The car just isn't in a great position to see down the road. Tesla has to deal with that same limitation.
There's a reason these problems stick around.