It's relatively efficient compared to alternative currently available approaches. We have not reached a point where Khan Academy and Udemy can replace everythin

It's relatively efficient compared to alternative currently available approaches. We have not reached a point where Khan Academy and Udemy can replace everything - or even a major part - of education after basic literacy and numeracy. The model of turning a literate child loose in a library and letting them be for six or eight years should not be assumed as universally useful.