I agree it's not a silver bullet doesn't begin to address the issue where students aren't learning because of issues they're dealing with outside of school.

I see this as Khan Academy x10. It'll be a great tool for those for whom Khan Academy itself was a good tool. If it's free (or for a nominal free), then parents will use it at home with their kids as a supplement to school. Teachers might use it on a case by case basis with students who want to accelerate or who are behind. It will highly accelerate learning for those who want to and are able to learn. The problems you describe, which are very real and important, are social problems, not educational problems per se or problems solved with technology.